Sometimes I may show my cards, either one or both, it all depends on what I want to achieve from showing them, if I feel the time is right to show a bluff, to make my opponents think I am doing it more than I should be,other times I may show only one card to prove I had something like top pair, but keep them guessing what my other card might be.
Usually though I only do it once I pass the bubble, because if I show the winning hand after the flop, I feel it is a show of respect to my fellow players, they earned it by getting as far as me, and once I achieve the money, I really don't care that much, Poker for me is a hobby, and if it cost me nothing to get in the money, I am more than happy to show my cards.
I try to keep my play friendly, and have a little fun, otherwise what is the point of playing?
When the fun Stops, STOP!