poker etiquette

I'm a very new holdem player and have a question. What is the proper procedure/etiquette for revealing your hand in holdem. For example, after the river, one player places a bet and the other players call the bet, does everyone have to reveal their hands or is there a certain order in which the hand should be revealed?

usually the person who places the bet must reveal their hand if they are called.

g/l

first to act should show... athough with an allin there is no hard fast rule that says the cards should be turned, I personally like when the cards are turned adds a ton of excitement to the hand

This is correct, the caller then has the option to muck (throw his cards away) if he knows he is beat.

A rule we have in our club is when all players in the hand are "all in" You MUST flip your cards up! I'm not sure about the WPT or WSOP. I have never seen a hand on TV where someone didn't show their hand after all players in the hand were all in.

Person who made the bet shows. Take the saying "Paying to see the hand" for example. Player A makes small river raise to entice a call...player B pretty much knows he's beat, but due to the small raise and in order to force Player A to show what he had, player B calls the raise in effect paying to see the hand of his opponent. Player B paid for the information for future reference.

If there are more than 2 players in a pot, the first person to act shows then the order technically should go clockwise as did the deal, one caller at a time.