"Being nice to bad players
Along those lines, here is an important piece of advice: don't berate bad players. When a bad player makes an incredible catch to beat you, you will be tempted to explain to him (if not yell at him) exactly how lucky he was, that he only had two cards in the whole deck that would win the pot for him, and how could he call your raise cold on the turn?
Remember, it is the bad player from whom you make your money. If you get him upset, he may get out of a gambling mood or, worse, leave the table. Now you can't win his money. Astonishingly enough, this ill-mannered behaviour toward lucky bad players is common. Instead, you should be particularly nice to bad players. When somebody puts a terribly bad beat on you, swallow, try to relax, and say in the calmest voice you can manage; "Good Hand."
Also, berating bad players (or anybody, for that matter) is just poor manners."
/Lee Jones