GamePro have some tips for you survivors out there, check them out:

#19: Leading is Not Cheating

In Left 4 Dead, it doesn't matter if you're playing as or against the walking dead--leadership is essential to your survival. It's a good idea if someone takes the lead at the beginning of every round. And seeing as this is the most dangerous job in your team, you may want to leave this role to more advanced players. It's crucial for the leader to know the ins and outs of the maps in the game, including where the safehouses and checkpoints are. And most of all, leaders should act as point man and damage tank.


#18: Know Your Role

Aside from the leader, the rest of the team acts as scouts and sharpshooters. Stay close to the leader, but scout out adjacent rooms (quickly) for health, ammunition, and bombs. Don't shoot people in front of you if you are acting as the sharpshooters.


#17: Cierra la Puerta

When playing as a human, a good habit to have is closing doors behind you. Zombies can smash through them, but it will hold them off for a good amount of time.

You can find more ways to survive right here.