Coop Expert strategies

In an effort to up our game play level, here are some tips:

1) In expert mode, friendly fire is your worst enemy. Make one person the established leader (and point man). Where the leader goes, the other 3 follow. Know where your friends are at all times so that you are less likely to shoot them in the face.

2) Travel in a consistent formation. This will reduce friendly fire incidents a great deal, because you have an expectation of where your teammates are, even when you have to turn to shoot at a charging zombie. A commonly suggested formation is this:
The leader and a buddy travel crouched up front with assault rifles and/or shotguns. The other two travel standing with assault rifles and/or scoped rifles. This will allow the standing players to fire over the heads of the crouched, and the crouched can melee incoming hordes. Others suggest an offset diamond, with the point man crouched. Still others don't recommend a formation at all, but just to stay close. Either way, consistency of team member placement in relation to one another does seem to help a great deal.

3) If a teammate gets incapacitated, he should be close if you are doing your job. Friendly fire damage appears to be disabled when a teammate is incapacitated by a hunter or smoker, so blast away. But fire in short bursts so you don't damage your teammate when they are released.

4) If you are getting mobbed by the horde, crouch down so an assault rifle teammate can headshot the infected's heads around you. If your teammate is getting mobbed and you are close, jump in and start meleeing, shooting away from your teammate. 3 players can stand over a downed teammate, melee the horde off while shooting away from the center.

5) Follow a wall so you are not out in the open. You have less time to prepare for a horde in expert. The trick is to fall into an easily defenable location when the horde hits.

6) If you are indoors and a horde is building, let the leader (pointman) pick a place where your backs aren't vulnerable. If in a hallway or up against a wall, 2 crouch and 2 stand with the wall at your back, each set has a 90 degree arc of responsibility. If in a corner, each player has a 45 degree arc of responsibility. (Again, assuming no tank is around.) The best place to be (if there is no tank around) is a small room or closet. This strategy is frowned upon in versus, but used often in expert coop if the goal is to be slow-and-careful as opposed to speed runs.

7) If you see a hunter that is far away, gun him down. If the hunter is close, melee him away and then shoot while he is stunned. If you start to shoot a close and crouched hunter, he can pounce on you before you get enough shots in him.

8) TANKS - like the intro movie says "run or shoot?" - "both". The mass consensus seems to be this: If you have room to maneuver, every player has > 40 health and you are in a location where there are attractive places for the tank to climb (NM final, DA final, barn area on BH final), light the tank up with a molotov and run. Let the fire do its damage over time. Run around obstacles so the tank takes time to climb or throw. He will be faster when on fire, but again, if you have the space to offer him distractions, this is the way. If a teammate goes down from a tank fist, they are dead - don't try to save them (as much as it may pain you). Get distance on the tank with options for exit in case he comes after you and blast away. If your maneuverability options are not optimal for this or you can not run due to low health, do NOT light the tank on fire. The consensus is to run to a location where you can offer him distractions (like the rooftop crane area on DA). This seems to be the most debated strategy.

9) In each group, there should always be one person with a molotov (for strategy 8) and one with a pipe bomb (for surprise hordes in locations that are not optimal). Do not waste these assets in easy areas.

10) Don't burn through your health packs and pain pills. 20% or lower for health packs - some people will argue that you should be in the "black-n-white" before using a health pack. Since pain pills can be administered quickly, save them for when you need them - when a tank shows up or for a final sprint to the safe room.

11) Don't take a health pack if you have teammates there that need it more - or take it and heal them yourself when they get less than 20%. That means DO NOT heal up when you reach the safe room, then take another when the next round starts. Remember that keeping your friends alive keeps you alive.

12) Some experienced players asked to be team-killed near an exit safe room if their health is below 50%. They would prefer to die and be respawned with 50% health for the next section, as opposed to starting the next section with a low health and possibly needing to burn through a health pack. I myself think of this as an exploit of sorts (this wouldn't happen in real life, since there are no respawns), but others argue that there wouldn't be a zombie apocalypse in real life. If you are ok with this strategy, it can help your team be more successful.

from: http://forums.steampowered.com/forums/showthread.php?t=809871