Winning poker comes down to being able to squeeze a profit out of marginal situations. The object is not to win every hand played, but to win every hand you play. The best way to do this is to out bet your opponents. Every bet made should have a purpose. Either it is made to induce a weaker hand to fold, or it is made to maximize the winnings on the hand.
Since there are many opportunities to outplay your opponents, you have to know which opponents you can outplay. It is difficult to finesse weak players. The slow play often backfires because...