There are, of course, a few key things to always remember: * Stop, look, and listen. * Being observant might alert you to something nasty ahead of time, like a Witch, Special Infected or Tank, and allow you to prepare yourself. * Teamwork. * This cannot be stressed enough. Left 4 Dead is supposed to be a cooperative game. Communicate with your teammates, if you're playing with others, or if you're by yourself with the AI, point out things they might otherwise miss. In all cases, watch out for each other and take care of each other. You are not going to survive the zombie apocalypse by yourself. * Be ready for anything. * Don't panic.