Don'ts

Do not point out your opponent’s luck, or lucky rolls, either during or after a match. Whether you mean to or not, pointing out your opponent’s luck suggests that he is winning or has won due to that luck and not due to his skill. Even if he was unbelievably lucky, it’s poor form and bad sportsmanship. And most players fail to see their own good luck as well as the many bad rolls the opponent probably got too. Most players also forget that the better you play, the luckier you seem to be, because you are set up for more good rolls and protected against more of the bad rolls. When a player tells me how lucky I am just after I've beaten him, I say "Yes, I was lucky to play someone who played so much worse than me."
Do not call your opponent’s bad rolls, or your own good ones. It’s irritating and capricious.
Do not handle the doubling cube unless you mean to double. In fact, this could even be, consciously or unconsciously, a form of cheating ... you reach for the cube and see if the opponent reaches for the score sheet or reached to take the cube ... or simply check out his reaction.
Do not roll until your opponent has clearly picked up his dice. Rolling too soon, or just as he’s picking up his dice, can only create conflict as to whether or not the roll counted, or whether or not the player had truly finished thinking about his play. And quick rolling unfairly rushes the opponent into playing.