Vampiric Musings, Or How Do I Kill It, And Why Does it Work?

I've been thinking about the standard ways to kill a vampire. I've got a few questions:

Stake to the heart:
1. How much of the heart has to be pierced? Is it a square hit to the center, or will a slight contact that's completely surrounded by heart tissue do?
2. How much of the stake has to be wood? Is it the entire thing, or will a metal tipped one, such as an arrow do? Does a completely metal-shod wooden stake count?
3.Why does it work at all?

Burning:
1. How do you get them to catch fire? Does it count if they simply grab something hot?
2. How much of a vampire must be burned? For example, if you burn a vampire's hand off will it heal?
3. Does sudden, non-prolonged, contact with flame such as that from an explosion kill a vampire if none of the other conditions are met? If so, why?

Sunlight:
1. Why? Just, why?

Also, this will be part of a series of posts titled "How Do I Kill It And Why Does It Work?". This won't cover everything, only those with some special methods of killing them, instead of, or in addition to, the standard means. Each post will be two parts: In the first I ask questions, about things I don't get about the ways you can kill something, and in the second, I post the best responses to those questions with the author's name/identifier being listed. Suggestions for what I should do next, if they include a list of weaknesses, are welcome.