Since this thread has been going on since July, and some have posted dozens of replies since, I'm going to fudge a bit and give you my Top Five All-time Poker Nuggets.
1.) The most overvalued, overplayed hand in Hold Em is AK. Without help, it's nothing but Ace-high. A pair of twos beats it. Never go all-in preflop with it, not even in heads-up play. If you don't flop any help, muck it.
2.) The key to winning any tournament is SURVIVAL. Make it a rule to only play AA, KK, QQ, or AKs in the first hour of a tournament. You can't do anything but lose a tournament in the first three hours. Your primary goal should be to reach the final table, not to climb the leaderboard.
3.) The best way to mask your play is to adopt standard opening bets based upon position. Early position - 2 x BB. Middle position - 3 x BB. Late position - 4 x BB. If you have a relatively weak opener in early position, you can easily muck it if raised. If you have big cards, you can re-raise. If you bet preflop by position, no one can ever put you on a hand, because you're betting AA preflop just like you're betting 78 suited.
4.) When playing stud, if you can't beat what you can see...fold. Period.
5.) When playing High-Low, never enter a hand playing for the LOW. The most you can win is a chop. Always come in high and play for the scoop. (Note to "wheel" fans: the A-5 straight only scoops in Hi-Lo about one time in five, even if you hit it. The rest of the time, it loses to a higher straight, flush, or boat, leaving only the low chop.)