Sit n Go Strategy
Sit 'n Go tourneys are fast-paced and fun to play in. It's like playing in a microcosm of a big multi-table tourament. The structure of SnG's is usually that of a one-table freezeout and the top 2 or 3 places pay out. Since you're going to be starting out with at least 9 or 10 players at your table, it makes sense to play pretty tight in the early stages of these tournaments.
Early Rounds
The blinds start off pretty low in these tourneys, so what do you have to gain by bluffing, or even playing a mediocre hand at all? You're not going to be picking up much if you win the pot, and you might even get raised to the point where you're paying much more than you'd like to. Wait until your table is a few opponents short and the blinds are higher, you'll have more to gain by playing aggresivley.
Middle Rounds
As the blinds begin to increase further into the tournament, you'll need to open up your play a bit. Firstly, you'll want to start looking for tighter players to steal the blinds from. As the tournament progresses and the blinds become a larger percentage of everyone's stack, play at the table will generally tighten up. You'll often find yourself in late position without any players yet to enter the pot. If you have a decent holding (two face cards, an Ace, or any pocket pair), you should consider raising to gain control of the hand and possibly win the blinds preflop. This play works best against tight or timid opponents, who will usually fold unless they have a premium hand. If this type of player calls your raise or reraises you, you should be careful. They're tight players, so a call or raise means that they're holding a strong hand.You can still attempt to steal the blinds from aggressive opponents, but tend to have a stronger hand to raise with than you would against tighter opponents in case you get called or reraised. Unless you're holding an overpair to the board, I don't recommend a continuation bet against an aggressive. This type of online player will often call you down with middle or bottom pair, and if you can't beat that you shouldn't bet.
When To Fold
So When Should I Fold?
There are two major decisions to be made at Limit Hold'em. The first is preflop, whether to play your hand or not, and the second decision is to be made on the turn. The flop decision isn't really that important being as most of the time you'll just be making or calling a small bet.
The second major decision is on the turn. Let's say you call the turn, you should call the river because it would be a definite disaster to fold the winning hand on the river. Calling the turn and the river means investing two big bets, equalling out to four small bets. Let's assume the pot is raised preflop and just one bet is made postflop, you would have only invested three bets to see the turn. Therefore, you can fold at the turn and lose slightly less than half the money you would have lost had you called to a showdown.
The river is not the time to fold your hand. The only exceptions to this rule are when you missed a draw (such as a small flush draw) or if there is so much betting and raising that you know you are beat.
No-Limit Texas Hold'em Common Mistakes
Not folding a decent hand when beat, thus losing all chips on one hand.
Calling with weak cards when facing a bet.
Playing way too many starting hands.
Not raising pre-flop with premium hands and then going too far with them after the flop.
Over or under betting the pot (risking a lot to win small/not protecting hand
Bluffing
In most Texas Hold'em games played, structured (limit poker) is the most common type of poker played. Unlike no limit, where you can shove your stack all-in, your bluffs will be limited to a single bet or raise more often than not. Because of this limited betting, bluffing randomly can get you in trouble, BIG trouble, as your opponents will most of the time be willing to call down a single extra bet (especially in low limit games). As good as it may sound to tell yourself that you're going to bluff everyone out of the next hand no matter what, it's not going to work the majority of the time.