Kill 1 Lurker.
The first Lurker you encounter will be in the basement of your house when trying to get to the backyard into the Cemetary.
These guys are easily dispatched with melee weapons.
Knife: Use an A,A,A,X combo then evade backwards, then repeat.
Pipe/Axe: Use an A,A,X combo, this will knock him down for a few seconds, then use a charged X attack, this will usually result in an exploding head :)