I've read that you never show if you don't have to. I can see if its a friendly game, then showing is up to you. But the idea is to keep the other players guessing. If you show them when you DO have a hand, then they might not want to call you later on when you want them to. And vice versa, if you show them when u do not have a hand, then they might be willing to call ur bluffs in the future. It's just safe to always muck and keep them guessing. Make them pay to see your cards.