First of all, you need to find a friend and convince him/her to dressing up as a vampire, in this way your role will be more credible. For help your friend, you could suggest him/her to visit www.instructables.com and search for halloween's suggestions.

Once you have convinced your friend, you can proceed with your incredible dress. The apparel must be casual so if you are a guy find a jeans and a t-shirt , if you are a girl is recommended to wear something really sexy because the vampire are very selective in choosing victims.

Attended the dressing up, it is good to prepare the mental side of the dress to playing the role very well. It's known that when somebody has been bitten by a vampire, the victim goes trough the vampirization : he/her looses consciousness, dies and reborn vampire. Therefore, you have to try to faint in front of a mirror or a camera an try to reborn vampire to play the role in the best way. Then, you will become a real vampire's victim for the other people.

The most important thing in your dress is the make up. The vampirization is a very traumatic experience : you should put on some make up to make your face more white, a blue or violet lipstick for the lips and make the dark circles. You have to seem like a dead man live.

In the end the thing making your dress unequivocal is the vampire's bite on your neck : everybody will know that you are a vampire's victim and they will congrats for your genial idea!
So, take a red marking-pen and draw 2 little circles on your neck... the distance between the 2 circles should be like the distance of the fangs of your vampire's friend. You should also draw the blood gushing from the bite. The blood quantity depends on how cruel your bite have to be.

Have fun!