Aim for the vulnerable spots to use your munitions most effectively, though some zombies will require more than one shot to retire. If you shoot a zombie as it is rising from the ground, only one shot is needed to take it down.
Reloading your weapon takes time, so plan your reloads carefully! If you have just one bullet left and there is no immediate danger, fire that bullet and reload before a new wave of zombies appear.
Game inspired by short story by Howard Philips Lovecraft.