Research which Twilight vampire you wish to dress as. You can dress as one of the members of the Cullen family: Edward Cullen, his siblings Jasper, Alice, Rosalie or Emmett, or his parents Esme and Carlisle Cullen. For a more dramatic look, dress as a member of the Voluturi, an ancient vampire council who wear richly colored robes and costumes.
Apply a pale foundation make-up to your face. No matter which vampire character you choose, you will need pale skin. Remember that the Twilight vampires are not cartoonish or ghoulish looking, but have very pale skin, so be sure to apply the make-up accordingly.
Apply a body shimmer cream to your face and any other parts of your body that will be exposed. The one thing that sets Twilight vampires apart from regular vampires is their ability to sparkle in the sun. Do not try to be subtle with your application. Even if you end up much more sparkly than the vampires in the movie, you want your sparkles to show so that people will recognize your costume.
Put together an outfit based on your character of choice. The Cullen family wear regular human clothing, but each individual has a specific style. Edward, for example, usually wears plain, muted colored pants and button-up shirts, while Alice would wear something more trendy along with a fabric choker. For Rosalie, wear something sophisticated and form-fitting. If you choose to dress as a member of the Volturi, purchase or make a hooded, velvet robe.
Style your hair to mimic your vampire of choice. Meyers is quite clear in her description of each vampire's appearance, so each character has a specific hair color and style. Use temporary hair dye to match Edward's copper hair or Alice's darker hair. If your own hair is not the right length to mimic that of your favorite Twilight character, buy a fashion wig that matches Alice's signature pixie cut or Rosalie's flowing blond locks.