Best way?
Stand around for about 45 mins to an hour and just watch.
It takes alot to learn to play craps, but you can get the basics and make or lose money easily enough.
Stay away from the sucker bets, or odds bets until you become more familiar with the way the game is played.
first toss is called the Come Out roll. If you roll a 7 or 11 you win and the round is over before it started. If you roll a 2, 3, or 12 that's a Craps and you lose: again, it's over before its started. Any other number becomes the Point. The purpose of the Come Out roll is to set the Point, which can be any of 4, 5, 6, 8, 9 or 10. The Dealer places a puck marked "On" above the Point number printed on the table.
This is about all you need to know to get started, and then, just watch what other people are doing, and try to figure out why they are doing it.
Good Luck, and dont take your rent money.
