Don't Flash Your Private Parts To Strangers
Don't show your cards. Ever. Even if you have a royal straight flush and everyone else folds and you're just dying to show this once-in-a-lifetime hand... just quietly muck the cards and move on. Showing your hand almost always does more harm than good. I used to have this show-selective-cards leak in my game, thinking erroneously that it would lead my opponents to think I was one type of player when in fact I was playing a different style. Fortunately, Mr. Multi straightened me out, and I have not shown a card since then. Remember that poker is ultimately a game of incomplete information. Whomever has the most information has an advantage, so why would you want to give your opponents any extra advantage? Showing your winners when you don't have to just tells the opp what kinds of hands you play in different situations and positions. Showing your losers reveals the exact same thing. Even selectively showing specific weird hands to your opponents in the hope that you can use this info later in the game really just means you have to keep track of what you showed to whom, why, when, etc. In other words, this is another form of Fancy Play Syndrome. Don't do it. Keep all your flashing to back alleys and street corners, where it belongs.
All-in for now...