How many pucks are used in an NHL game?
On average about 12 Hockey Pucks are used in a NHL game. Ref's carry more then one and once they thaw they replace it at faceoff's.
The NHL rules are too many and too involved to list here. I would suggest you go www.NHL.com and check out the rulebook yourself. Also, you can simply Google NHL rulebook or NHL Official Rules. You should also remember that, while hockey is hockey, a number of rules/regulations used in the European/international game are different from the NHL pro game.