6max SnG strategy is significantly different to full ring strategy. In full ring it's standard to take the cautious early approach and pick up the aggression as the blinds increase. In 6max the blinds come around a lot quicker so you need to keep up the pressure on the blinds right from the word go. Most 6max SnGs pay the top two places so you still have the typical three or four stages to the SnG.
Early Stages Middle Stages / Bubble Play Money Play
6max SnGs are all about pressuring the two blinds. The blinds come round very quickly so you can not afford to sit there waiting for those big hands because you will simply be blinded into oblivion. You should be raising with a very wide range on the button and in the cut off to keep your stack competitive with the others. Also bear in mind that other players will be raising a wide range in those seats, so if you think the time is right then you can open your 3betting range to steal bigger pots. A good 3betting range consists of:
Suiteed Aces Pocket Pairs High Switched Connectors
Obviously whether you 3bet or not is very dependent, doing it just for the sake of it is not going to win you many chips in the long run. You need to target the players who are opening very often from late position. You can use the 'Note' feature in the poker client to keep tabs on who you can 3bet lighter from the blinds. If called pre-flop then you must proceed with caution post-flop.
Suited connectors pre-flop lose their value slightly in 6max, mainly due to the more aggressive nature and with it also being harder to get involved in multi-way pots. It is usually a better idea to raise with these type of hands with the intention of stealing the blinds, and when called, a well timed continuation bet will often do the trick.
Middle Stages / Bubble Play
By this time you have probably lost one or two players, so the blinds are orbiting quicker and also vastly increasing. Now is the time to benefit from a bit extra aggression. The button and cut-off positions are now almost a mandatory raise with a very wide range. Only absolute trash should be folded when you are in these positions.
When stealing blinds you will also need to consider everyone's stack size at the table, especially if you are on / near the bubble. A very short stack to your right is ideal because if it's folded around to you, any raise all-in from itself can only be called by really big hand or a really big stack as it would not make sense for a player to gamble all or nearly all of their stack when they have a less than 100% chance of winning the hand. As a high percentage of the time the short stack will be the next player eliminated.
Pressure the blinds from the word go. Raise with a wide range on the button and in the cut-off. Consider 3betting a late position steal from the blinds. Suiteed connectors are not as valuable. When one or two players are eliminated and the blinds start increasing, raise almost every button and cut-off. Consider opponents stack size at all times.
Once you are in the money (assuming top 3 are paid), you should really up the aggression so that you will either be busted in 3rd or go into the heads-up stage as a comfortable chip leader. The reason being is the difference in money between 1st and 2nd is significantly larger than the difference between 2nd and 3rd. So it would be more beneficial finishing 3rd from trying to hit that heads-up stage with the chip lead which if successful, should get you a 1st place finish a decent percentage of the time.
Once you are in the money (assuming top 2 are paid), you should rarely limp in the small blind unless you are trapping an aggressive player. At the heads-up stage the small blind has position so you have the advantage in the hand from the word go. It is generally bad to let the big blind see a free flop by being able to check. Pressure your opponent into making a mistake! You should also tighten up your range in the BB as you are out of position and are immediately at a disadvantage in the hand. Forget hands like fitted connectors in the BB, concentrate your range more towards high cards.
Shove nearly every hand on the bubble when you are a comfortable chip leader and there is a short stack. Consider opponents chip stacks at all times. Open shove a wide range on the bubble if there is a short stack. Be aggressive when the bubble has burst. Aim for 1st place and do not be afraid to go out in 3rd place from trying. Do not limp in the SB when heads-up. Tighten your range in the BB when heads-up. Suitted connectors lose their value when you are out of position.