In Texas Holdem, your position is extremely importance. Since Texas Holdem has four rounds of betting, the position is even more important than in other forms of poker.
The rule is that you should play fewer hands when you are in an early position and more hands in a late position; you should also play the same hand differently in different positions.
The later you play, the more information you can get from the other players and thus the more capable you are of making better decisions.
The decision of whether or not to play a hand has a lot to do with the type of game. In a tight game (when there aren’t many players in the flop) you should play fewer hands than in a loose game. If there are many aggressive players at the table, you should also play fewer hands than if you are playing against many passive players. In general, in Texas Holdem and in other forms of poker, the greater the competition is, the fewer hands you should play.
Some hands, like AA, don't like many opponents because if there are 4 more players, a pair of Aces has less than a 50% chance of winning, even if the other players have marginal or weak hands.
A JT suited or small and medium pairs like a lot of opponents because if the JT hits his card (flush, highest straight, set, etc.), the player with the second best hand will make him win a big pot.
From these examples, you can see how important is it to know how the other players play. This information will come in very handy when you have to make a decision to fold, call, or raise.
Playing in last position gives you some unique advantages: being able to steal the blinds when nobody has bet, getting a free card, semi-bluffing, and more.
You can find specific guidelines in different books about how to play every hand preflop in Texas Holdem by your position. Some of them are great books by very good writers, like David Sklansky. However, I don’t believe in following guidelines automatically; you should understand the principles behind making a decision based on your position, and then act according to the situation.
Examples:
1. In an early position (first to third player), play only your very good hands, like a high pair and high suited connectors. A hand like K9 is not a playable hand in an early position. In a loose game without many raises preflop you should probably play with – pairs: AA, KK….66 suited: AK, AQ…A2, KQ..KT, QJ, QT, JT, JT, T9, T8, 98, 97, 87, 76 unsuited: AK, AQ, AJ, KQ, KJ, QJ, JT, T9
2. In a middle position, you should play more hands than in an early position. In addition to the hands played from early position:
Pairs: 55…22 suited: k9, K8…K2, all other suited connectors like 65, 54, 43 and some of the one gap connectors like 86, 75, 64, 53 unsuited AT, KT, QT, J9, T9, 98
3. In a late position (on the button or close to it from the right), you should play more hands and more aggressively. When there aren't any raises, you can play almost any hand in a loose game, and should raise even your mediocre hands if the game is short-handed.
Suited: any two gap connectors like T7, 96 or even three gap connectors like T6, 95 Unsuited: any connectors like 87, 76, 65, 54, and gaped connectors like Q9, J8, T8
Just remember, there are no automatic guidelines. You should adjust your play to your opponents and the situation.

Article Source: http://www.articleset.com