A fellow wrote these and posted them on RPG.net. Being as I've been trying to promote non-selfish gaming for a long time, some of these really strike home. The original thread can be found here, if you're so inclined.
Anyway...thanks to Ratboy45 for posting these. I think they're pretty neat.
A good player will think about what his character would do before he acts.
A great player will think of ways to make his character realistically take actions that benefit the game.
A good player will seek out opportunities to get his character involved in things.
A great player will seek out opportunities to have his character help others get involved.
A good player will avoid doing things that makes the GM's job more difficult.
A great player will look for ways to make the GM's job easier.
A good player will make an effort to learn the rules.
A great player will remember that the rules must sometimes be broken for purposes of flavour or story.
A good player will seek out ways to build his character's story.
A great player will know when to let his character’s story end.
A good player understands that winning means having fun.
A great player understands that winning doesn’t mean much unless everybody wins.
I may even go over the ones I really like, as well as I why I really like them, later on. Right now, I'm a bit too mentally drained to even consider doing that.
Note: I edited the format of these a little bit.