Left 4 Dead Basic Survivor Tips

Above all else, STAY TOGETHER. Zombies love love love to pick off the stragglers. If you must leave the group for some stupid reason, make sure you have a buddy with you.

Talk. Lots. L4D forces team play, much more so than any other game I've ever seen. As survivors, you are easy prey and easy to find, so talk to make sure everybody leverages what advantages you have. This includes telling your team mates about weapon locations, coordinating who uses health packs, and notifying each other where special infected are located.

Call for help. And keep doing it. If you get pounced or tongued, make sure your teammates know. They may be busy and can't get to you right away, but don't give up on telling them you've been caught. There's a lot of chatter, you want to make sure you get heard. A dead or incapped teammate is WAY worse than an annoying chatterbox.

Distribute your weapons. A balanced loadout has two survivors with shotguns and two survivors with machine guns (SMG or AR). If your team is 1337, the ideal advanced loadout is two auto-shotguns, one AR, and one hunting rifle. But I don't think anybody is that good yet.