kill.vampires
How to Kill A Vampire
Stake through the heart
When a "direct hit" is scored, this is very effective. Vampire immediately explodes into dust. (Too many examples of this to list here. Just watch any episode.) Apparently, it doesn't have to be a traditional whittled stake, either. Buffy is a very creative Slayer when it comes to staking vamps. She's used pool cues, chair legs and signs before to get the job done.
Exposure to direct sunlight
When vampire flesh is exposed to sunlight it begins to smoke, then burn. It seems to vary how long it takes for the vamp to explode into dust with this method.
(See "Becoming, Part I" for a demonstration of a vampire exposed to sunlight - Buffy refers to it as an immolation-o-gram)
Beheading
Another excellent method, explodes into dust, immediately.
(See "The Yoko Factor" for an excellent demonstration by Adam)
Holy Water
Much the same as direct sunlight. A little will sizzle the flesh, but it would probably take a drowning in it to kill. (See "The Harvest" to see Darla demonstrate the "sizzle effect.")
Buffy also tricked a vampire into drinking holy water which incinerated him from the inside out - for an example of this, see "Helpless".
Starvation -
One would assume that if a vampire was unable to feed for a looong time, this would eventually kill them. Obviously it would at the very least weaken them. After re-watching Season Four episode Pangs again - Spike mentions that a vampire that doesn't feed becomes emaciated. It might not kill them - but it would definitely weaken them. Spike is weakened by just a few days without feeding.
The Bible
Works the same as the cross and holy water - It causes them to "vamp out" and burn. A good example of this was just shown in Are You Now or Have You Ever Been. One would assume you would have to get a lot of exposure for it to kill. Perhaps you could beat a vampire to death with a Bible, or bury one under a pile of them? Who knows...