Tips and tricks

First of, forget anything you know about combat. Zombie warefare is completley different from anything you have ever experinced, I guarentee it. Only use melee weapons as a last resort, and try to keep the Zacks at as far a dictance as you can. They can't bite you if they are no where near you. Wear lightweight armor only, Heavy armor will only slow you down and if they bite through that you are screwed anyway so think "What will allow me to manovure the fastest?" Know the layout of the building you are in. Memorize where the weapons, medacation, and exit routs are. Be sure you have multiple escape routs planned so in case one is comprimised, you have another escape route. Do not spray ammo in to zombie crowds even if you have a automatic weapon! Aim and make every shot count if your weapon is automatic, switch it to semi-auto, Warning: While you should make every shot count, do not take to long aiming. This will just stall you and bring you ever closer to your death.
I will be adding more tips as I can think of them.