Position at the table, or where a player sits relative to the dealer, is one of the aspects of poker most often overlooked by rookie players. They mistakenly think that all seats are created equal, and that what matters most is what cards you have in your hand. This couldn't be further from the truth-- as Norwegian wűnderkind Annette Obrestad demonstrated, professional players know "how important it is to play position and to pay attention to the players at the table"-- Obrestad won a sit and go game online where she looked at her cards only once (on an all-in) during the entire tournament.
The best position that you can hold in a poker game is the one where you're the last person to act, i.e., you get to make your decisions after observing everyone else at the table as they make theirs. In poker lingo, you're said to "have position" on any players who have gone before you (those who have already taken their action by the time you take yours) and you're "out of position" with those who come after you (those who can take your actions into account when considering your own). This is because there is a distinct advantage to having a position that allows you to go after the other players, and a distinct disadvantage if they end up going after you. Generally speaking, you have position on the players to your right and are out of position with the players on your left, although certain circumstances can change this. If your opponent has the button, for instance, or you are to the left of the blinds on the first round of betting, you are out of position with them.
Position in a poker game is generally broken down into early position, middle position, late position, and the blinds.
The first three players after the blind generally comprise early position (although obviously, all of the positions shift depending on the total number of players at the table). In Texas Hold'em and the majority of beginner-level poker varieties, the general rule is that the later your position, the better, so early position requires a player to really be careful about what cards he or she plays. When you're in an early position, you don't want to move forward with a weak hand, because you have no control over the betting and will likely lose unless you have the nuts.
In games like Omaha and Stud, early position offers certain advantages-- meaning that it's not all bad news if you're stuck in an early position. However, there's a lot more strategy involved in these poker variants, and you need to know the strategy that is specific to these games and think on your feet to really be successful. As a beginner, though, you can just stick with "early is bad, late is good" and stay away from Omaha.
Under the Gun (UtG)
If you're under the gun, or UtG as it's commonly abbreviated in poker circles, you're sitting in the earliest position at the table. This puts you at a strong disadvantage, because you have to decide how you're going to act before anyone else, and they will all be able to take your action into account when making their own decisions. The number of starting hands that are actually worth playing from this position are very few-- when you're in this position, you don't have a lot of leeway and will probably end up folding the majority of hands that you get (if you're playing right).
Middle position generally refers to players who are after the first three players after the blinds and before the last two players before the blinds-- i.e., any players who are not early position or late position. Middle position isn't ideal, but it's not too bad, either. Since most hands of poker get whittled down to just a couple players at the table (as the rest have folded), you'll still have position on any of the players who go before you if you end up in heads-up play with them. In middle position, you have greater freedom in terms of which hands are actually worth playing, although your options aren't as wide open as they are in late position.
The last two players before the blinds are generally considered to be in last position, the most advantageous of positions in a poker game as you can assess everyone else's actions and go from there. If you're adept at tells and knowing when other players are bluffing, you might have a good idea of what other players are holding in their hands by the time your turn to bet comes around. If you're in last position, you have a lot more options in terms of what hands you can actually run with.
Being in a late position in the game offers you the opportunity to claim the pot if other players have flopped or hesitated to bet before you. By betting in late position, you have the chance to bluff and push other players out of the running, therefore claiming the pot for yourself. If you don't have a particularly strong hand, you have a chance of taking the pot, but you should also be willing to bow out and fold if someone else raises after you. This is called a check-raise (when someone checks, hoping for another player to raise, and then re-raises), and it's often used to trap players into committing to a pot for which they don't have a strong enough hand. The value of this last position also varies if you're playing something other than Texas Hold'em-- while it still has value, being in the very last spot (the button) makes it very difficult to pull off a solid raise in games like Omaha HiLo and some varieties of stud.
The button, which designates who the "dealer" is during a particular hand, is widely considered the strongest position at the table because this individual is the last one to bet in each round (except the first, when the blinds go last). This not only gives the person with the button the most information for making decisions, but it also puts him or her in the prime betting position, allowing them to bluff in order to drive others out. When someone raises on the button pre-flop, it's called a button raise, and experienced players are likely to notice if you make button raises too often, which will counteract their efficiency when other players start to call whenever you bet from this position.
Big and Small Blinds
There are benefits to sitting in the blinds, but mastering the balance of the strengths of these positions with the vulnerabilities that they also have is the key to playing them well. Players in the blinds have already contributed to the pot-- either half (small blind) the minimum bet or all of it (big blind)-- before the round of betting starts. During the first round, the small and large blinds bet last, but they bet first every round after that. This means that the blinds have the advantage during the first round of betting but lose it quickly thereafter and will find themselves in a more vulnerable position. Since players in the blinds have already thrown money into the pot, they essentially get a look at the flop for free (or half the normal cost), which is a very strong advantage.
What many beginning players fail to understand about playing the blinds is that this advantage isn't permanent. Many players don't fold when they should while in the blinds-- a lousy hand is still a lousy hand and holding onto it isn't going to make it any better-- and they often fail to assess their cards as someone sitting in early position should (more allowances are made for late position, and many novice players in the blinds will assess their cards as though they were sitting in late position, which becomes a regrettable move as soon as the first round of betting is over and the player's hand loses some of its relative strength). Other beginning players will call raises made by other players, thinking that the difference isn't too great. Such players take for granted that the money for the blind isn't "free money"-- it's something they've already coughed up for this round-- and they're more willing to throw good money after bad by calling a raise made by someone with a better hand than they have.
When playing the blinds, always remember to be conservative-- while there's no harm in checking and seeing the flop (if you're the big blind), don't get too attached to the cards that you have while in this position, or you may end up throwing money away. Statistically speaking, players lose more money in the blinds than they gain.