No Swearing
Use nice language.

Dealer or Player Abuse
It's simply not polite.

Playing Slowly
It's not fun for the other players when they have to wait forever for you to make a decision. Some people use this as a tactic to make other players nervous.

Splashing the Pot
Throwing your chips into the current pot is rude because it makes it hard for people to see what your bet is. Stack neatly.

Acting in turn
Refrain from a betting action like folding your hand, until the action comes to you. This gives information to people before their turn to act.

String bets
This is another jerk tactic to create a response in the opponent. Only grab the amount of chips that you intend on betting, so not to make the other players think you're betting more than you actually are. Place them in one action, don't string out the bet.

Hitting on the Other Players
Regardless of whether or not you've never seen a poker player that hot before, you should refrain from hitting on the other players at the table.

No Comments During a Hand
It's not appropriate to make comments about possible hands being played regardless of whether you're in the hand. This can give unfair advice to less seasoned players. This is especially true when talking about your hand or the cards you just threw.

Intentionally Avoiding Blinds
Games like Hold 'Em and Omaha, where blinds are required, it is not appropriate to leave the table intentionally whenever it is your turn to pay your blind. Some players use this tactic to avoid an unfavorable betting position.

Don't be a Jerk