Poker is a game of continuous learning. There's never a point when you can say "I know everything" or feel that your game is perfect.
This is why having an online poker coach to improve your sit n go game is so vital. A good SNG coach can evaluate your current play, fix 'leaks' (weaknesses) and improve your strengths further. The sort of things a SNG coach may look at in a poker coaching session -
1) Your starting hand ranges - maybe it's too wide and you're playing too many hands in a sit n go. Or, it could be the opposite and you're playing too tightly. Hand ranges need to adapt according to the stage in the sit n go (i.e. tighter in the early stages and opening up later on) and also to the opponent (tightening up if you're playing against a 'donk' for example).
2) Your bet amounts - are you raising enough, or too much, pre-flop? Are you taking into account limpers in your raise size before the flop? Then on the flop, with 'cbets', are you betting as frequently as possible? Do you know when and when not to cbet? A good coach will check you're getting good value for your premium poker hands like a set.
3) Your endgame / shove/fold - a good knowledge of shove/fold on the bubble is vital in a sit n go game if you're going to be profitable over the long term, even more so if you play turbos where the blinds increase more steeply. What is correct ('equilibrium' play) can be explained mathematically. Now, some of this may not make sense at first (e.g. spots where it's profitable to shove any two cards and spots where you should be folding AKo). A good online SNG poker coach will explain the reasoning behind it (probably whilst using the poker software Sit N Go Wiz), giving you a feel for what hand ranges you should be pushing or folding with.
4) Your headsup (HU) game - when you're down to two players ('headsup'), now is the time to play to win. You can play a much wider range of cards, and aggression is vital. On top of that, any connection you have to the board becomes far more likely to be the winning hand at that point. Getting a great SNG poker coach means you can learn a good headsup game, exploiting the probable weaknesses of your opponent.
A great sit n go poker coach will adapt their teaching to both your own style of learning and your own learning needs based around your current poker game. For poker coaching to succeed, you need to be open to taking critiscim both from your coach and yourself. Taking the ego and emotion away from the learning process is important as it means you're then open to evaluating your own SNG play on an ongoing basis, perhaps using Sit N G Wiz (SNG Wiz) and/or Holdem Manager, If you're relatively new to the game then I'd recommend downloading Ace Poker Drills, a great, simple piece of poker software that helps you learn things like odds and hand ranges.
Summary
Every poker player who is committed to improving and succeeding in their poker goals needs a good poker coach. Finding a good one and being open to being critical about your SNG skills means you stand far more chance of being a profitable sit n go poker player. Whether you're after a poker coach to help with your 6max SNG game or after a multi-table sit n go coach,being coached will help you crush the game and move up the stakes.
Good luck at the tables and be sure to check out the sit n go poker coaches on this site.