1) Stay on the move. Barricading yourself in = death.
2) Never carry more than you can comfortably pack. Being slow = dead.
3) Don't bother with melee weapons unless you're willing to die. If you can melee them, they can melee you.
4) Always carry a melee weapon. If you don't, you're screwed anyway.
5) If you see one zombie, avoid it or kill it. If you see more, run.
6) Don't expect anyone to watch your back.
7) Guns don't kill people. Guns kill zombies. ^_^
Guns run out of ammo though, so don't get ****y.
9) Get the hell out of town. The greater the population density, the greater the potential threat.
10) When using melee weapons, avoid bladed weapons. Blades chip, break, and get stuck in bone. It takes a LOT of strength to cut off a head. On the other hand, kinetic energy does amazing things when applied via a lead pipe.
11) Never assume any place that's been populated is safe. If there were people there, there are probably zombies there now.
12) Get on top of something that'll allow you to still move. Like Rooftops. You can climb, they cannot.
13) If they can climb or run, you're screwed.