Vampires:
Also known as: Nos Feratu, Vampir, Vampyre

These demons take a prominent place in "myth", and are recognized in many cultures. The European version tends to be the mot recognized, though, and that one will be that most information will be relevant on, unless otherwise specified.

A vampire is, technically, a human corpse that has been possessed by a demon. This corpse is taken over by the demon, and the personality, memories, and everything about that person is then altered by it. The Demon molds itself to look, act, sound, move, and think like that person, except for one thing. No soul. With one televised exception, no vampire has a soul, and thus, has no deep need to do what's right. In it's place, a sense of survival, and malevolence. Vampires drink the blood of animals, but if they can, they will always choose a nice, juicy human. Vampire reproduction isn't anything like a human. They drink most of your blood, and just as your heart begins to slow, they force you to drink theirs. It is thought that vampirism carries a virus which travels through the blood, and thus makes this transfer necessary. After you die, your soul is lost, (some would say destroyed, or sent to Hell/Heaven), and your body is possessed by the vampiric demon.
One night following that event, usually at midnight on a full moon, you will rise again as a vampire.

Methods of Destruction:
There are four basic ways to destroy
1 a vampire. The most well known is a wooden stake through the heart. The conditions for this vary greatly from culture to culture. Some say that anything composed of wood will kill a vampire, as long as it passes through the heart. Others, most notably, the Europeans, say it must be aspen or poplar2, and some even say it must be blessed by a priest. Another way is rather common to demon hunting, and can be applied successfully to most demons. Decapitation. Beheading a vampire was
one of the  most often used back in the medieval times, but with the advent of guns, this method has taken a severe drop. Also, putting a vampire in direct sunlight will destroy it. It is thought that because the sun has many "godly" relations such as Apollo, Ra, and even some obscurely thought relevance in Christianity (sun = son), rays from the sun are thought to be holy enough to damage, and after prolonged exposure (on the order of seconds), destroy them. The final method can be very, very dangerous. Setting them on fire, and burning them to death. For this, you put yourself in more danger than any other method, because all they'd have to do is touch you for a second, and you'd be on fire, too.

Limitations:
A vampire can not enter a mortal residence unless it has been invited. Once invited, it can return any time it wants, and there is very little you can do to stop it. You could try an uninviting spell, but that can be tricky. Also, you could try a security system that fires wooden stakes, but that may be dangerous for the family cat. 8-)

The Chinese & Japanese
3 cultures say that if you spread grains outside your residence, a vampire will be compelled to stop and count every grain. If you spread enough, they will be counting well into dawn, and be destroyed.

Vampires can be damaged in a number of ways. Limited exposure to sunlight, garlic, anything that has been blessed or is a symbol of something holy (crucifixes & holy water are best known), and among some cultures, objects of silver.


FOOTNOTES
1 I use the term "destroy", because vampires are undead, and therefore, already dead, so you can't "kill"
them

2 Aspen and poplar are two woods, often considered to be the same thing

3 Japanese culture had few vampires, but when one did appear, it was said to come from China. The most
notable was Chirayoju, and for more information, see "Buffy: The Vampire Slayer, Blooded", or consult a
historian of that area (period in history, and area).