Blood:
The symbol of life since ancient times. Blood only flows in the living and since vampires are undead, they need blood for sustenance. It is their only source of energy and food.
Fangs:
Vampires must drink blood in order to survive. Their canines are elongated, sharp and protrude enabling the vampire to pierce the skin and jugular vein while feeding.
Vampires can have retractable fangs too but Buffyverse vampires' fangs only show while the 'feed' is upon them, along with their true Demonic visage.
Fingernails:
Vampires' fingernails are usually sharp, elongated and resemble claws. However, The Master had fingernails like claws except Angel, in his human form, seems to have regular nails.
Skin:
Vampires are usually pale since they can not go out into the sunlight. Buffyverse vampires seem to have a healthy complexion in their human form but their demonic selves are a tad pale.
Hair:
Vampires usually have the same hair and length as they did when they were 'reborn'.
