The six available levels you will fight for are enclosed locations, divided into named areas that will appear onscreen as you enter them.
Typically, your objectives during the third, sixth, and tenth waves are going to take place in randomized locations, with the final extraction wave always occurring at a set location.
Because of the changing nature of how the enemy arrives in every level and the randomized objective locations and modes, you will have to be more flexible in how you approach these battles.
Survival Tips
Communicate
Communication is probably the most important piece of advice in any multiplayer game. With no radar to easily track the movements of your enemies, locating them is entirely up to your own eyes and ears.
Your teammates may have missed that Phantom that slipped around to the side, but if you didn’t, you should probably let the rest of the group know that cloaked death is nearby.
Communication also allows for you to properly set up defenses, coordinate Biotic or Tech combos, and conserve the few consumables of each squadmate.
Even before an actual match, teammates should let each other know what sort of firepower they are packing, the equipment they have, and what class they prefer to play as.
A team that communicates will almost always fare better than one that doesn’t.
Stick Together
Any enemy will die faster under a combined assault, and your chances of being rescued from being downed dramatically increase when a squad is actually working as a squad.
Unless your team is supremely powerful or supremely confident, there’s no bonus for being a lone wolf, particularly during late-game waves where a single player will be very hard pressed to deal with everything headed their way.
On higher difficulties, bleeding out is a real danger for loners, because the action is usually too hot for your teammates to risk making their way to you.
Stay Mobile
You obviously don’t want to be running around while under fire, but it’s a good idea to not be tied down to one position unless an objective calls for it.
Even then, you should know what your options are so that if your little piece of real estate is about to be overrun, you know where you can fall back to, and where you can go to flank the enemy.
If for whatever reason you’re the last man standing in a squad, or you’re trying to complete a map solo, staying on the move is your best chance of survival.
Keep Your Head on a Swivel
Your enemies are not only aggressive, but also fairly smart. They will seek alternate routes to any location a player is bunkered down in, and they will ambush you from behind if you become too focused on what is directly ahead.
Scan your surroundings once in a while to prevent unpleasant surprises.
Short, Controlled Bursts
With the Spare Thermal Packs and the ammo crates lying around each level, you effectively have infinite ammunition for any gun you bring.
That doesn’t mean it’s always a good idea to hold down the trigger and spray at advancing foes. Make sure you’re hitting what you are aiming at.
Running out of ammo in the middle of a firefight is a potential death sentence on any difficulty, so make what you have count.
Make Constant Use of Your Powers
With the weight system giving bonuses to power cooldowns if a player is packing light, their powers can be almost constantly available. Take advantage of this.
A Vanguard being able to constantly charge, an Engineer spamming Cryo Blast or Incinerate, or an Infiltrator cloaking to boost every sniper shot, this all serves to boost how much damage you do to every enemy.
Conserve Items
It might be tempting to use your Ops Survival Pack the moment you get low on health, or to immediately pop a Medi-Gel as soon as you hit the ground, or to blast that lone Assault Trooper with a Cobra missile, but try to make these resources last into the final waves of any mission.
An ally can help you up, and an Atlas might be more deserving of Cobras.