Step 1: Things Required
a headcrab hat (or any headcrab that can fit on your head)
a blood-stained white long sleve shirt
a blood-stained pair of blue jeans
you can get fake blood at any halloween store or you can make it yourself (there are instructables on how to make fake blood).
Step 2: Blood Staining
Step 3: Walk Like a Headcrab Zombie
here is a video of headcrab zombies
Step 4: Talk Like a Headcrab Zombie
yabba, my light meh
heres a video of the sounds headcrab zombies make
Step 5: You're All Done
now go scare your friends.