In a single-table tourney, your chip stack (how much cash you have compared to your opponents at any given point) relative to other players is the most significant aspect of the game.
Chip stacks bears a substantial impact on the hands you wish to play and the method you bet those hands after you jump right into the pot.
Determining your chip stack
To fully understand your chip stack, you should consider a few factors:
Pay attention to opponents with big chip leads or those falling quickly behind; both have a moderate tendency to over-bet the hand. If you have a superior hand, you shouldn't be afraid to go up against those desperados; in fact, you need to raise when you have the opportunity to show you are serious about that hand.
Leading a single-table tourney in the initial stages does not do much for you, other than the mental comfort that usually comes with knowing you are not losing the game.
If you ever find yourself down after an early knock or two - particularly if an opponent knows that you are bluffingguard the blind if you have mediocre hands. Once again, you want to conserve your chips to use them only if they can bring you more chips later.