Re: Ideas on showing appreciation to your GM
Every GM likes to provide fun for the players. An occasional 'this is a great game' can preen a GM's feathers, but mainly, as the others have said, the best thing you can do for your GM is to keep his/her game running.
Post frequently, letting people know about absences, post inclusively, offering hooks for your fellow players rather than closed one-liners, develop your character and create opportunities for others to develop theirs, interact with each other IC, answer each other's IC questions, pick up on hooks and comments left by other PCs, have your PC's actions offer opportunities to lead or follow others rather than forming a collection of solo players,be a team player.
A game like that is more fun for you and your GM.