Gaming is a social contract. Everyone has agreed to show up and spend their time participating to the best of their abilities.
Just as the GM has agreed to not (intentionally) create a situation which automatically wipes out the party, or precipitously violate the framework of the imaginary world by having German tanks roll out of the Elven woods, _you_ the player agree to try to play the game, and to play it in a way that not only satisfies your own creative urges but also works for everyone else who has committed to spending their time this way.
There are three ways a player can violate this agreement. They are the three sins of players:
being a passive audience
being a saboteur
being a critic
Passive audiences listen more than they take action. They sit quietly while the GM describes the scene, but then just keep sitting quietly when they are supposed to participate.
Saboteurs take actions or raises issues that block the game. They may adhere to a strict character concept that doesn't permit them to actually go on the adventure (slavish roleplaying) or they may do things like go on spontaneous solo missions and leave the other players sitting waiting.
Critics points out flaws in the game. They might be rules lawyers or plot perfectionists, or just the people who needless point out how much the game seems derivative of some movie or book they read (double points for any comparison to Star Trek).
These sins are often rooted in the best of intentions. Very few players intend to harm the game, but misguided help can result in harm.
By being interested in the story of the game and listening attentively to what the GM tells you, you risk being a passive audience. After all, no GM likes a group that can't sit still for a minute and listen to a description.
By including conflicts and dilemmas or adhering to your character concept, you risk being a saboteur. A good roleplayer wants an interesting character, and an interesting character enhances the game. A completely bland character can fit anywhere, but what's the point?
By wanting the game to be better and pointing out possible improvements, you risk being a critic. The flaws in the game may be quite serious and need fixing. Most GMs will claim they would prefer to get this kind of feedback rather than have the players suffer in silence (and potentially get sick of the game).
These positive behaviors are valuable and even essential for games, so it isn't so easy to just say “oh well I'll never do that.” You may start helping the game and slip into committing a gaming sin before you know it. I'm never guilty of being passive, rarely a saboteur, but probably a critic more than I should be — a sin that stems from my constant urge to improve the game.
What about you?