Read the Poker FAQ - Frequently Asked Questions about Poker
(by Kevin and Mike): It is vitally important to know what the "average" winning hand is in the various games we play. For example, you might think that your Flush is going to kick everyone's butt for high in Pass The Trash; however, repeated play has shown that the typical winning high hand for that game is a Full House or higher. In fact, we've seen cases in that game where two players both had Straight Flushes! It gets even crazier with wild card games like Follow the Queen or Suffecool, where Five of a Kinds are frequently seen. Never be afraid to ask players at the table what the "typical" winning hand is for a game you are unfamiliar with. It may save you some bucks in the long run.
(by Kevin): It is okay to get up and "take a breather" at any time, especially after getting hit with a particularly nasty bad beat. No one expects you to play in every hand, and cooling off for a few rounds is better than staying at the table and playing "Angry Poker".
Check out Mike's Recommended Reading List
Read this article about poker books from Poker.com