Sit n Go tournaments are very common on many poker websites.
In the single table variety of these tournaments, six or ten players are usually needed to open the competition. The basic idea is that all players are simultaneously present on a single table. Most of these tournaments start at a fixed time and need the fixed amount of players in order to begin. There is a certain poker strategy that goes into playing these tournaments which will be described here.

In a Texas Hold'em variation of a Sit n Go tournament, for example, you have to remember that it is important to have patience and restraint so that you can reach the final heads up game.

This is not a regular cash game where you can afford to gamble on whatever the flop brings. The stakes are much higher here. The most common strategy is to begin by discarding all your weak cards. Make a raise three or five times the big blind whenever you get a favourable hand.
This will prevent others holding weaker hands from getting lucky on the flop.

Remember that your element of surprise will diminish in the later stages of the tournament, where your opponents will already be aware of your approach, and would rather fold to you.

At this point, focus on stealing the blinds, which will by then have increased to a very large amount. This will be a great boost to your stack of chips, and also keep your opponents off your back. Also consider whether it is a 10-people tournament or a 6-people one.
If the first, you will definitely reap benefits with the poker strategy described above, since the bubble will be at the fourth or third place. If you are up against only 6 people however, you should remember that you will be investing more into the blinds, as they will reach you more frequently.

To counter this, you should try stealing the blinds occasionally in the early stages itself, so that you will be insured against any later loss. Be aggressive but cautious. Target players with smaller stacks and force them to go all-in or fold. On the other hand, be careful enough to fold when you are uncertain. You do not always have to re-raise your opponents.
Make long term strategies in Sit n Go. Do not be tempted to limp in with poor cards even if the blinds are low, as you will be forced to call at some time or the other and will have no chips to gamble on. So play this enjoyable variation of poker keeping these tips in mind.