Players are expected to verify registration data and seat assignments, protect their hands, make their intentions clear, follow the action, act in turn, defend their right to act, keep cards visible, keep chips correctly stacked, remain at the table with a live hand, speak up if they see a mistake being made, transfer tables promptly, follow one player to a hand, know and comply with the rules, follow proper etiquette, and generally contribute to an orderly tournament.
-- POKER TOURNAMENT DIRECTORS ASSOCIATIONThis rule says a lot. The most used portion of this poker rule might be that the player is responsible to protect his own hand. Some people use a card protector for this purpose.
Rules Version 2013 TDA Rules Version 1.1, released August 11, 2013
Overall the rule says "be nice". This is the origin of the F-bomb rule. There are dozens of "rules" and principles in poker that can be derived from this rule. Each poker room may apply this differently, but everyone is still about the same.