Also, kill games only occur in LIMIT games, never in no limit. For example, in a 4/8 game, a full kill would increase the stakes to 8/16 for a kill pot, while a half-kill game would increase them to 6/12.
As Double-A said, kill rules vary per casino, but in general, in a limit HE game, a player winning two pots in a row triggers a kill pot. In Omaha hi/low, kill games are popular, and they are usually triggered by a player scooping one pot over a certain amount.
For all kill pots of all games, the player who triggered the kill pot gets a "kill" button in front of him and is required to post a big blind (at the new higher stakes), regardless of his position at the table. If he wins again, the next hand is also a kill pot (but the stakes do NOT increase again), and he is required to post again.