Howcast and Big Fish Games list some tips for making zombie outfits that include ripped old clothing, face paint and liquid latex. The main keys for a basic zombie outfit are fake blood and torn clothing. Zombie prosthetics can also be added to enhance the costume.
The first step to making a zombie costume is finding some old clothing that can be torn and stained with makeup or fake blood. Old clothing and clothing found at thrift stores are some options. Create a shriveled face with liquid latex by stuffing the mouth with cotton balls and applying the latex. When the latex dries, remove the cotton, and the latex shrivels. Use white makeup to create a deathly pallor on the face or anywhere else. Add some light blue makeup to further accentuate the pallor. Darker blue makeup creates a hollowed-out look.
Use liquid latex again to create the impression of torn skin and then add fake blood for a gory wound appearance. Other colors such as purple, brown or red add to the effect. Add to the zombie costume with other prosthetics such as fake nails or teeth. Another easy way to stain clothes without using fake blood is to use ketchup, Kool-Aid or red food coloring.