Popping zombies' heads
The easiest method to decapitate a zombie is, when you are equipped with the Shtogun or Assault Shotgun, let them get close to you, aim up and fire. Instant decapitation.
There is another method that works for both the Shotgun/Assault Shotgun and the Handgun. Press the auto-aim button (L if you're playing the Gamecube version, Z if you're playing the Wii version) and fire at an approaching zombie normally. You have about a 1/6 chance to decapitate the zombie with the Shotgun/Assault Shotgun and about a 1/10 with the Handgun. This tactic should only be used with the Shotgun/Assault Shotgun if you are fending off multiple zombies and can't risk letting the whole lot of them get too close for the usual method. This is highly useful with the Handgun, though.
Note that decapitated zombies will not return as crimson heads.
Added by: Volke Dec 31st 2009, ID#8991