KILLER POKER

Play Aggressive Poker
While I wouldn't call myself an expert, I think I have played enough to make some helpful observations to the relative poker newcomer. I play in a weekly game with some coworkers, where we usually do a single table no-limit Hold'em tournament, and I have participated in a few low stakes multi-table tournaments online. The following advise is probably best used in low stakes tournament settings, but I think they probably apply elsewhere.
I think the single most important approach you can take to a game is to be aggressive. The aggressive player sets the tone, and can usually control the action for a given table.
Before I go any further, let me explain what I mean by being aggressive. Aggressive play and loose play are not the same thing. Aggressive does not mean betting every hand, or always staying in a hand to the showdown. In fact if you are going to be aggressive, you should probably not play as many hands as most of your opponents. Being aggressive means that rather than calling, you would raise, rather than checking, you would bet, and when you bet, bet more than the token minimum allowable bet.
Since this strategy requires you to wager more in the hands that you do play, you have to be more selective in those hands. You don't have to win the most pots to come out ahead; you have to win the biggest pots.
One situation where you would want to consider aggressive play is pre-flop from a late position. If you are going to play a hand, why not raise pre-flop rather then just calling? Force your opponents to pay to see the flop, and build up the pot that you are planning on winning. Betting pre-flop will also represent a strong hand which can be used for bluffing after the flop, if the flop doesn't help you. If there were many callers pre-flop, then raising, will either increase the size of the pot when other players have to call your raise, or force them to fold, eliminating the chance for them to back into a hand later on.
Another example is when you think no one was helped by the flop. Often lesser players will simply check around hoping to get a free card to help them out on the turn. In this situation, the person that bets first will often win the pot, because everyone else will fold. Betting post flop from an early position could also be a defensive move. If you have an average, but not great hand, consider betting instead of checking. Weaker players that may have bet had you checked will often just call rather than raising you. So by betting a small amount, they become tentative, and don't try to push you. And if they had nothing, they may fold rather than staying in to try to back into a hand on the turn or the river.
When you play cautiously you allow your opponents to control the hand and capitalize on your weakness. By being the aggressor, it is you who determines how the hand is played out, and what the ultimate stakes will be.