I never seem to find the time to watch Jeopardy! often enough, myself, but if you're a Jeopardy! head (or even just a Maphead), you might enjoy Ken Jennings's article on Arthur Chu: Arthur Chu Is Playing Jeopardy! the Right Way.
In any game of Jeopardy!, three clues have been secretly earmarked as Daily Doubles. The player who finds each one can bet any or all of her winnings on responding to it correctly. By and large, Jeopardy! players are a risk-averse bunch. Unless a player is in need of a big comeback, the Daily Double wager is usually a smallish one.
Strategically, this is crazy. Like a poker player trying to increase the size of the pot when he has a good hand, Jeopardy! contestants should maximize their upside when the odds are in their favor.