This content was taken from the /r/mecoop wiki page on reddit

OVERVIEW

This guide covers the known and speculated mechanics of the Mass Effect 3 Multiplayer Store. Rather than a detailed breakdown of each pack type, the guide analyzes the value of buying different types of goods (e.g. consumables, Ultra-Rare weapons) with respect to pack type. The values are mathematically obtained through the cost / mechanics of the pack. There is a degree of uncertainty on some numbers - the guide will disclose when that is the case. Finally, the guide covers some suggested buying strategies and tips.

For clarity and brevity, this guide uses some abbreviations and terminology. For packs: Recruit Packs (RPs), Veteran Packs (VPs), Jumbo Equipment Packs (JEPs), Spectre Packs (SPs), Premium Spectre Packs (PSPs), Arsenal Packs, (APs), and Reserve Packs (ResPs). 'Consumables' refers to Rockets, Medigel, Ops Packs, and Thermal Clips. 'Items' refers to Characters, Weapons, Weapon Mods, or Gear, and 'Equipment' refers to Ammo (e.g. Incendiary II), Armor Modules (e.g. Cyclonic Modulator III), and Weapon Amps (e.g. Shotgun Rail Amp I). Finally, Ultra-Rare is abbreviated to 'UR'.

PACKS

Each pack has five slots, except for the JEP, which has 10. Each of those slots can unlock only certain classes of goods. For instance, the first slot of every pack is dedicated to unlocking consumables (or equipment when consumables are maxed), and the last slot of every non-JEP is dedicated to items or equipment.

The following table shows the cost and content of each of the packs.

There are some exceptions to the equipment levels, and those occur when you have maxed certain portions of your manifest (e.g. all your Uncommon Weapons or consumables).

CONSUMABLES

The following table shows the expected number of consumables earned from each pack type, per million credits spent.

Lower-tier packs unlock consuambles at much higher rates. In particular, JEPs unlock consumables at a 12x rate when compared to PSPs, APs, and ResPs. If you're low on medigel or rockets and you are desperate for a quick boost of consumables, consider some of the lower-tier packs. JEPs obviously offer the best value, but for other reasons (covered below), you may want to choose another pack like a VP.

Note, the '+' on JEPs in the table is because they often unlock a '+2' consumable in one of the equipment slots in addition to the 4 '+5' slots. Unfortunately, not enough data has been collected to determine the actual rate at which these '+2' consumables drop. Regardless, JEPs offer by far the best value for consumables alone.

EQUIPMENT

The middle slots of packs most often produce equipment, but they can produce other goods such as 'Reset Power' Cards or Common Characters (even if you have maxed them). Item slots (the most rightward slots) can also unlock equipment, in particular when you have maxed a part of your manifest. For instance, if you have maxed your Uncommon weapons, the right-most slot in a VP will usually give you level III equipment instead (the other two middle slots will usually give you level II equipment). Likewise, in an SP or PSP, the item slots will give you level IV equipment if you have maxed your Rare weapons and characters (unless you get an UR weapon).

The following table shows the expected number of drops of each equipment level, per million credits spent. It ignores middle slots that drop items instead of equipment (for reasons that are explained below). For higher-tier packs (SP+), it also assumes maxed Uncommon Weapons. The question marks in the table indicate values for which there are insufficient data to draw conclusions.

The '-' symbols in the table account for items that will drop in place of equipment. Generally speaking, based on the data available, these drops occur at <=25%, and they appear to hit each pack roughly proportionately. So, while the numbers in the table may not be accurate in these cases, the relative value in the packs should be roughly correct. A '50' has more value than a '50-', which means that VPs are technically the best pack for maximizing level III equipment once you have maxed your Uncommon items.

Notable takeaways from this analysis are that level III equipment drops at nearly equal rates in VPs, JEPs, and SPs. Higher-tier packs (i.e. ones that cost 99000) are an inferior option for unlocking combined level III and IV equipment compared to SPs, especially for players with maxed Rare manifests. An SP for a character with a maxed Rare manifest will unlock level III+ equipment 33% faster in SPs than in the more expensive packs. Still, a VP with a maxed Uncommon / Rare manifest will gain more than double the volume equipment (2/3 of which will be level II), when compared to SPs.

ITEMS

The table below shows the expected number of item drops per million credits spent. URs have been skipped for this analysis, as they are covered below. There was insufficient data on unlock rates for Uncommon Characters / Weapons, so the table assumes those have been maxed. It also assumes that none of the Rare items have been maxed.

* Small sample size

The conclusion here is that for any Rare item, SPs and PSPs appear to have similar buying value. This may be somewhat surprising given that SPs have half the Rare slots but at 60% of the price. It appears this can largely be explained by SPs unlocking Rare Mods in their 4th (non-Rare) slot rather frequently. Once you have maxed your Rare Mods, PSPs will offer a better value for Rare Items. But if you're leveling up your entire Rare manifest, the two packs will offer nearly identical value for Rare Items. Given the benefits of extra equipment and consumables from SPs, they may offer a better overall value.

VPs are by far the best value for Uncommon Gear, but SPs, counterintuitively, offer a better value for Uncommon Mods. It's advisable to mix in some SPs early on to help unlock these Mods.

Arsenal Packs are an intriguing option for someone leveling up their manifest - you can make progress on Uncommon Items at a decent rate while leveling up your Rare Weapons and Gear. Unfortunately, they do yield very little equipment, and as with all 99000 credit packs, the yield on consumables is very low.

ULTRA-RARES

This is the topic that is of most interest to many people, and unfortunately, the data collected does not offer any definitive conclusions with respect to the best packs for unlocking UR weapons, for a number of reasons. First of all, there is nearly incontrovertible statistical evidence that the UR weapon drop rates can change. Data collected on day-of-DLC has shown drop rates doubling for UR weapons in PSPs, APs, and ResPs. Secondly, obtaining estimates of low-probability events is much more difficult than for high-probability ones.

That said, the current best estimates of UR weapon drop rates in non-DLC time-frames are 7.5% in SPs, and 15% in PSPs, APs, and ResPs. Given the cost of SPs is higher per UR, these estimates project that you will unlock URs about 18% faster with the 99000 credit packs.

You should take these numbers with a grain of salt, given the potential statistical error. The SP numbers are seemingly the most reliable, as they have the largest sample, and there has never been evidence that the UR drop rate has changed in them. For the other packs, it is very possible that numbers reported have been biased by day-of-DLC effects. If the true rate for the 99000 credit packs is somewhere closer to 12-13%, (as has been measured in the past for PSPs), then SPs and PSPs would have no difference in value for URs.

Note, UR characters appear to drop at a higher rate than UR weapons, though the exact difference is unclear based on the data collected. APs do not drop UR characters, and there is no obvious difference in the drop rate between PSPs and Reserves (though data is limited).

EDIT: UR drop rates have been confirmed to be 7.5% per Rare slot, so our speculative data was correct. You can expect an effective 7.5% from SPs and 15% from the 99K packs.

MISCELLANEOUS

• If your goal is to unlock more equipment, there is merit to saving your credits and buying packs in large spending sprees. The reason is that once you have maxed your consumables, packs will unlock equipment in their slots instead.

• Each piece of equipment has a maximum value of 255. If you go beyond that when buying packs, the value will be reset to 255 when you restart the game.

• Anecdotally, some Uncommon Weapon Mods do not appear to unlock through packs lower than SPs. After maxing your Uncommon Weapons, it is advisable to mix in some higher-tier packs (best to start with SPs).

• Upgrades to your consumable capacity can be unlocked through VPs and up. There isn't enough data to recommend which packs are most efficient for doing this (though it is likely that SPs and higher are best, as they offer more Rare slots).

• ResPs unlock Common Character cards 50% of the time in one of the equipment slots. This is effectively 100000 wasted credits for each million spent on ResPs.

• Among SPs, PSPs, ResPs, and APs, the latter is the only pack not to unlock Common Character cards. Thus, for someone with a maxed Rare manifest looking to maximize their UR chances, APs may be the best value.

• The store will only unlock items for which the associated DLC is installed. To boost the odds of unlocking a specific weapon / character, you can uninstall all other DLC except the one containing the target item (e.g. uninstall everything except Reckoning DLC to boost odds of getting the Collector Adept). Just be sure to install all of the DLC before trying to play again, or it will be difficult / impossible to find a match.

CONCLUSIONS

People frequently ask about spending strategy in the store, and the answer depends on their goals. For new players, it's advisable to max your Common inventory through RPs, as many of the Weapon Mods in those will be useful later on. As a next step, maxing your Uncommon Weapons through VPs will substantially increase the value of those packs, since level III equipment will begin unlocking instead of weapons. This equipment will be critical when moving up in difficulties.

That said, for maximum enjoyment of the game, a mix of packs is likely to be most gratifying. If you feel like unlocking new weapons, try APs. For new characters, try ResPs. Or, for a mix of equipment and characters / weapons / mods, stick with SPs or PSPs. The most effective buying strategies will involve keeping your supply of consumables and equipment at a decent level, while unlocking new characters / weapons for the sake of fun. A mix of packs will accomplish this.

This content was taken from the /r/mecoop wiki page on reddit

1. Getting started

ME Co-Op is first and foremost a team game. This means you live or die by the quality of your team. You need to work together in order to succeed, especially on the higher levels. The other thing you really, really need to learn from the beginning is that POINTS DON’T MATTER. The scoreboard is there, of course, but at the end of the match all points are aggregated and experience is divided equally. Points make you feel like you did more but they don’t really matter. Be a team player.

Each match consists of 10 rounds + 1 extraction round. Each wave is more difficult than the last. On Waves 3, 6, and 10 you will have one of five possible objectives.

Hack

You have to find the hacking terminal and activate it to start the hack. You must stand in the hacking circle in order for the bar to fill up. You have a limited time to do this. It is almost always the best idea for all four party members to stand in the circle and defend it. Four players hacking make the progress bar increase significantly faster. Enemies also spawn infinitely while you are hacking so the longer it takes, the more enemies you have to fight. Anyone who is outside the circle running around fighting their private war is almost always not a team player. Wave 10 hacking missions are widely considered the bane of all players’ existences. This is why it is so important for everyone to hack: the faster it goes the better off you are. Also, if you attract all the enemies to same place you can more effectively Cobra nuke them.

Capture

This involves running around the map and activating four different devices by standing there and holding down the activation button. The devices are randomly spawned around the map and must be activated sequentially. Strategies for this include all four players going to the device and guarding it while one player activates. However, a more effective strategy on harder difficulties is having one player, preferably a cloaked Infiltrator, activate the device while the rest of the team “aggros” (aggravates/draws the enemy into attacking) them somewhere else.

Assassinate

This involves sequentially killing four randomly assigned enemy units. You have a fairly limited amount of time to do this although you gain extra time for each assassinated target.

Collect Objective

This was newly introduced in the Rebellion DLC (May 29, 2012). This involves collecting two objectives, one at a time, and walking it back to the drop-off point. You cannot run while holding the objective, as you will drop it immediately if you do. If you are cloaked you will also immediately de-cloak. You can otherwise take cover and move normally. This is pretty straight-forward: one person collects and the others protect. The second objective spawns randomly as soon as you return the first one.

Escort

You must run to a designated spot on the map and activate a drone. The drone then makes it way to another spot on the map as long as a player is next to it. The drone moves faster if there are more players near it and the drone will periodically recharge your shields. Escort missions can be tough as it necessarily draws you out into the open.

You are awarded credits after each successful objective wave and bonus credits based on how fast you do it. Even if you all die and fail the mission, you will receive credits for the completed objective waves. Non-objective waves offer no credits at all. If you are incapacitated you come back to life at the end of each wave.

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The extraction wave is last and involves being in the extraction circle at the end of two minutes. It is not necessary to be in the circle for the whole two minutes, but you must be there at the end to get a full extraction experience bonus. There is 10% credit bonus for successfully extracting yourself, i.e., as long as you extract you get the bonus credits.

The game has four levels of difficulty: Bronze (easiest), Silver, Gold, and Platinum (hardest). The game’s default setting is to match you to ANY level of difficulty. Do yourself a favour and select Bronze when you are first starting out. Even after you have lots of experience, Bronze is the best way for experimenting and trying out a new class. There are fewer enemies, they are easier, and you will spend more time fighting and less time dead.

Winning matches raises your Galactic Readiness Score in single player. If you have 100% GRS in multiplayer, you get a 5% experience bonus per match.

2. Consumables

In the game you have 4 types of consumables, Cobra Missiles, Ops Packs, Medi Gels, and Thermal Clips. These are all limited use items. You carry a limited number into battle and these are drawn from your total pool of these items. Items you don’t use in a match go back into your pool but if your total pool is empty you won’t bring any into the match.

Cobra Missiles

These are Instant Kill emergency weapons. They will instantly kill any enemy they hit in a fairly large radius. They will NOT damage you or your team mates as there is no friendly fire. DO NOT waste these on small easy enemies or even large groups of easy enemies. These should be reserved for Banshees, packs of Geth Pyros, pairs of Phantoms, etc. Also, don’t waste Cobras when you are working on an Atlas or some other heavy and it’s the last unit. Just kill it with conventional weapons. If you are running out of time on an Assassinate objective, Cobras are very useful for quickly taking out an enemy. Cobras often miss if your aim is poor or there is a lot of lag. You can help yourself by firing at the feet of the enemy.

Ops Packs

These instantly restore your health and shields. Use carefully though. Sometimes there is a split second of lag and you may use the pack and still die. Take cover first. Ops packs can basically double your Medi Gel capacity if your timing is good.

Medi Gels

These instantly revive you when you are incapacitated. Be very careful using these as Medi Gels and Cobras are probably the most used items and therefore in the shortest supply. DO NOT waste these on wave 1 or by popping it instantly. It’s a good idea to keep spamming the spacebar (or equivalent) until you’re nearly out of time and then use it; this gives time for team mates to come revive you. Keep in mind that sometimes it is better to stay down. If there are two Geth Primes standing on your body, you will be killed instantly if you revive, so don’t waste your Medi Gel.

Thermal Packs

These instantly refill your ammo. You won’t likely use these much as ammo is generally plentiful around the map. However, try to space out where you refill as if everyone grabs ammo from the same crate there won’t be any until more respawns (usually 20-30 seconds?). Thermal packs also refill your grenades.

There are also weapon, ammunition, and armor powers that can be used to give you a bonus for the duration of one match. As of the new patch, there is now a description of what the bonus does.

NOTE: Weapon bonuses only apply to the specific weapon type. So for example, shotgun rails give bonuses to shotguns, not a shotgun damage bonus to any weapon. Ammo powers, however, do apply to any weapon you choose. thanks to JadeEmpress for this clarification

3. Characters

There are six classes of characters: Adept, Soldier, Sentinel, Engineer, Infiltrator, and Vanguard. Within each class are several different races. When you gain levels by earning experience, you level up the entire class not the individual unit. This means that if you level a Krogan Soldier to 20 (the maximum) then if you create a Human Soldier she will be level 20 automatically.

You put points into skills, just like in single player. Pay very close attention to the skills and which evolutions you want at skill level 4,5 and 6. Read about them from some of the many guides available online for the classes. Once you spend a skill point you can’t undo it unless you use a respec card (limited items) or promote the class.

At level 20, you'll have the ability to skill yourself with four skills at max rank with the fifth at no points. Most common builds will be something like 6/6/6/6/0 or 6/6/6/5/3. Note I'm NOT saying that's how you should spend your points for every class, just that most people either do max 4 skills or max 3 with 5 and 3 in the remaining two.

When a class reaches level 20, you can “promote” it. Promoting gives you +10 to your N7 score and gives you 75 war assets in the single player game. Promoting resets the class to level 1 and you must level it up again. Your N7 score is calculated from the combined levels of all your classes plus previous N7 scoring. N7 scores don’t necessarily mean much but can be a quick-and-dirty indicator of player “skill” or at least, experience in the game (time played). That being said, some people never promote so are very good with low N7 scores and some people are awful with N7 scores in the multi-hundreds. With the latest patch when you promote all the skills points for that class are unassigned, so you don't have the 1 default point assigned. This is a good thing.

Some classes focus on guns and some classes focus on powers, whether biotic or tech. There’s too much to write about that so here are some quick pointers.

• If you are a "casting" class, then cool down matters a lot. If you take very heavy guns you impact how fast your abilities are able to be used again. As powers are often much more powerful than guns it is not worth the sacrifice of powers to guns. Therefore, if you are an Adept, you generally should not be carrying a heavy shotgun or sniper rifle unless you really know what you are doing with it.
  • Low levels w/ caster classes: although this may sound bizarre it's actually better to overburden yourself with heavy/powerful weapons. Before you can put many points into skills, most abilities kinda suck. Having 200%/150% Cool Down Rate (CDR) doesn't matter much if you only have 1 skill and it's incinerate doing 200dmg. Might as well just take heavy weapons and not worry about casting at all. Not something you have to worry about right away but consider it when you start promoting. I normally do this for 1-2 bronze games until I get to about level 10, then switch to my normal loadouts and go to silver.
• Casting classes can setup combination attacks, either biotic combos or tech bursts. Basically, a combination is where one power "sets up" the combo and another power detonates it. Warp & Throw are very common as biotic combos, as are Reave & Pull. Combinations do a lot of damage in an Area of Effect (AOE) so are very valuable for getting a powerful explosion that will hurt several enemies. The most important thing to know about being a team player is to try to avoid shooting enemies that your team mates have set up for combos. This is more important on Silver and higher but get used to leaving warped/reaved/etc. targets alone unless they pose an imminent threat to you. As of the latest patch, tech combos (e.g., fire or cryo explosion, tech burst) trigger much more commonly. Like biotic combos, these occur when you use a setup and detonation power in a combo.
• Melee: melee-ing can be a lot of fun and is an integral part of Close Quarters Combat (CQC), which entails dealing damage to an enemy up close. The problem is that people often get very carried away with melee, especially Krogans and Vanguards and Krogan Vanguards. Melee-ing works very well on Bronze and it is often possible to kill most low level enemies with one or two melee hits. Melee-ing does not work as well on Silver or Gold. Use melee to get out of sticky situations or to finish off wounded enemies. But be careful that you do not find yourself on the other side of the map, alone, because you chased stuff to melee. If you go down in an inconvenient location, it is hard for allies to get to you.

4. Enemies

There are four species of enemies in the game: Reapers, Geth, Cerberus, and Collectors. Due to multiple fixes and patching, it is a toss-up which enemy set is the hardest. Geth are often considered unfairly difficult due to the stagger effect of many of their weapons. Collectors are also very difficult because of the combination of tough units and rushing melee units (which also explode). Reapers are still very difficult although the Banshee grabbing (instant kill) frequency has been reduced, apparently. Cerberus have been beefed up with some of their units, like the Atlas, getting buffs recently. The new Cerberus Dragoon unit is also very annoying.

You likely know about these guys from single player but here are a few notes that are especially pertinent in multiplayer.

• Instant Kill/One Hit Kill (OHK) Units: several units in the game can OHK you in melee range. If you are killed this way you cannot be revived that round. OHK units are Banshees & Brutes (Reapers), Atlases & Phantoms (Cerberus), Scions & Praetorians (Collectors). No surprise, DO NOT engage these units face-to-face in CQC. This is a recipe for being embarrassingly OHK’d. This also means the team plays the rest of the wave down a player.
• Tougher enemies have shields and armour. Know which is which and know which of your weapons/powers is most effective against which type.

5. Store

One of the most frequently asked questions is about which pack to buy. There are five packs: Recruit (5000 Credits), Veteran (20000 Credits), Spectre (60000 Credits), Premium Spectre (99000 credits), and Jumbo Equipment (33000) . Keep in mind that the approximate payout per successfully completed match type is: Bronze – 12000 Credits, Silver – 30000 Credits, Gold – 70000 Credits, Platinum - 110000 credits. Items are “cards” that are of four types: common, uncommon, rare, ultra rare.

Recruit packs usually contain two consumables (Medi Gel, etc.), one or two powers (ammo, armor, weapon) and one or two character or equipment cards (guns, mods, etc.). Consumables here are only +1.

Veteran packs usually contain two consumables but at +3, and then character and equipment cards, but with more chance to get a rare.

Spectre packs contain consumables at +5 with at least one rare card.

Premium Spectre packs are like Spectre packs but with at least two rares and a higher chance for ultra rare.

Jumbo Equipment packs contain +5 of each of the 4 basic types of consumables plus 3 additional random consumables.

It is often recommended for new players to buy lots of Recruit and Veteran packs to fill out your inventory of basic items first. This will help build your reserves of consumables as well. Weapons can be upgraded to level 10 and mods to level 5 so there are lots and lots of items that needed to be built up over time with cards. While everyone wants the ultra rare weapons, as a low level new player you shouldn’t worry about these yet. Focus on the fundamentals and earning some basic weaponry. For example, the Avenger X, the most basic assault rifle in the game, is still very useful even on Silver.

Note that as of the latest DLC, there are something like 400+ potential items to draw from. Compared to the beginning of co-op in March 2012, this is something like 200 more items. This means that completing items to V or X level is exceedingly difficult. The advice above about Recruit and Veteran packs may no longer apply as much.

Bioware ran promotion weekends in the past that often rewarded a player with an N7 weapon. These are the Eagle (pistol), Crusader (shotgun), Hurricane (submachine gun), and Valiant (sniper rifle). These weapons are now acquired through the same means as any other UR drop.

6. Final Pointers

The TL;DR for this guide can be summarized in one point: be a team player. Lone wolf/Rambo types are almost universally hated in this game, especially on higher difficulties.

If you are new, play conservatively. Find out who the best player on your team is and follow them around and support them. Take care of the Husk that’s after her or revive them if they're down. Stay in cover and shoot when there’s a good opportunity for it. The exception to this suggestion is if the best player is a Vanguard. Don’t follow them as the Vanguard will likely be zipping around leaving you exposed on foot.

If the rest of the team is just average, that’s fine. Stick together. Protect your snipers and casters or if you are a sniper or caster, stay with the group for mutual defense and help pick off the major threats or crowd control (CC) with explosions. Work with the group. Learn what people are doing well and not so well. Figure out what you are good at and what your style is. Practice that a lot.

And of course, POINTS DON'T MATTER. It doesn’t matter if you are last. If you are last but help out the team and don’t die in stupid places then you are more valuable than you know.

The game takes a lot of practice to get good at. Don’t worry about jumping up to Silver or Gold. Play Bronze until you can beat it comfortably even with a bad team. That’s a good indicator you are ready to move up. Also, seriously, don't play at a difficulty level you are not ready for. Everyone wants more experience and credits (usually just credits) but don't go playing Gold or Platinum if you aren't ready. You just end up being a huge liability to the team and look like a giant dingus.

Some final pointers:

• The green stain ravagers leave on the ground is a damaging pool of acid. Don't stand in it.

• If you disconnect from a game, it is possible to reconnect if you are playing on the PC and friends on Origin with someone in the game by clicking on their "Join Game" tab in origin -- but you will lose all the credits you have accumulated to that point. Likewise, it is possible to fill an empty spot in a game that any of your friends are playing this way. If you disconnect and reconnect using this method, it will refill your consumable allocations (e.g., you will be at your default number of medigels and hunter missiles).

• Different classes are stronger against different types of opponents. Adepts are strongest against Reapers. Infiltrators/Adepts/Asari Vanguards are strongest against Cerberus. Engineers/Infiltrators are strongest against Geth. However, every class is viable against every opponent when played with sufficient skill.

• Biotic explosion works against all enemies even if the persistent spell doesn't change the model of the enemy. E.g. your warp is persisting on a brute or banshee even if the brute/banshee doesn't look different, and can be set off with a throw/reave.

This guide was originally written for the mecoop subreddit by /u/anseyoh

UNBREAKABLE RULES (TLDR: Be Prepared)

• Open ground is bad. No radar and widely dispersed enemy spawn points mean enemies can get behind you very easily. Be mindful of that when you decide where to pick a fight. Catching a rocket in the ass is no bueno.
• Run and gun. Turtling up works for about 30 seconds to a minute. After that, every wave that spawned on the other side of the map will converge on you. The trick is to know multiple defensive positions and how to travel efficiently between them while hitting ammo boxes en route.
• Enter every fight with an answer to enemy barriers, shields, and armor. If your character's power kit has bonus damage against armor, then use a disruptor ammo consumable and/or an acolyte/reegar carbine. If your character's kit packs a lot of barrier/shield damage, use an armor-piercing mod and/or AP ammo on your weapon. IMO not having solutions to all enemy defenses is the single biggest reason people struggle in Gold+.

STRONG RECOMMENDATIONS (TLDR: Optimize your gameplay)

• Explosions are your friend. Certain abilities are "primers." Hitting an enemy that's primed with a different ability (detonator) will cause a powerful explosion. Some introductory combos: Warp > Throw, Incinerate > Overload, Snap Freeze > Incinerate. Once you get the general idea of how these work, I recommend you read this page to further your understanding of the mechanic. Until you get some Rare/UR weapons, mastering the primer/detonation is your go-to source of damage.
• tick together. The benefit of nearby teammates should be obvious. Teammates are an extra target, an extra gun, a revive, and an extra source of primers & detonators. However, if you find that your squad is breaking Unbreakable Rules #1 and #2 then fuck 'em, they ain't shit until they start following those rules again.
• Heavy hitters and where to hit them
• Kill the easy enemies first. There's a bunch of long-winded posts and explanations about wave budget, but really all it boils down to is "Kill the easy shit until no more easy shit spawns, then finish off the big guys." The exception is that objective rounds will continue spawning stuff until you're done with the objectives.

THINGS THAT ARE GOOD TO KNOW

• Everyone gets the same amount of EXP at the end of a match. Priority #1 is not topping the scoreboard - it's getting a full squad extraction. Topping the scoreboard is actually priority #2 :)
• You get credits at the end of every objective round and on extraction
• Armor does flat damage reduction, barriers & shields will recharge over time after a relatively short delay. This means that as a general guideline heavy hitting weapons are better against armor and bullet hoses are more effective against shields. Exceptions to this rule do exist.
• Buy veteran packs until you've got maxed out weapon mods, then just spam Premium Spectre Packs for sweet, sweet Ultra Rares.
• Use your consumables. If you're out of Shotgun amps, maybe it's time to switch classes and configurations so you can start chewing through your stack of SMG amps. Out of Phasic Rounds? Maybe change to a class with strong biotics and start packing a gun with armor shred attachments/rounds instead.