As a player in a social game, I recognize that the following contract (which until now has been unwritten) applies to my behavior and I will try to follow its standards as best I can.
1) As the fun of each relies on the fun of all, I will do my best not to design characters who have core problems with other members of the party.
1a) As a corollary to the first point, I shall not design a character who, before the game has even begun, wants to kill another PC for any reason.
2) As this is not a primarily thematic medium (in an Aristotelian sense), I shall refrain from making characters with unresolved issues that I can resolve throughout the course of the game and instead allow such instances to arise naturally, if at all.
3) I realize that not all evilly aligned people need to be assholes and can, in fact, be quite charming and pleasant. I will only play an asshole if my group approves.
3a) As a corollary to the third point, I realize that not all evilly aligned people would betray their closest friends and allies for a small material gain and I shall endeavor not to do so if I do decide to play someone evil.
3b) As a further corollary, I will not play an evil character if there is general outcry from my DM or group.
4) I shall engage in inter-character bickering and banter only to the extent that it is amusing and not to the extent that it actually splits the party into fighting factions.
5) Every one of these rules relies on the agreement of each player and I realize that we can collectively agree to break any of them at any time... but until such a time as that (when each party, including the DM) has vocalized a desire to break these rules, I shall do my best to abide by them.