Rules of the Rack
The word “rack” in billiards has a couple of different meanings: “to rack” the balls means to place the balls in a triangular frame (or diamond frame, depending on the game) in preparation for the break. Once the frame is lifted, the balls are considered racked. Then the frame itself is called a “rack.”
Racking the balls is not difficult — you just have to be careful to do it correctly. If you have a rack of fifteen balls, follow these guidelines:
Place the balls in the rack.
Align the apex of the rack (the first ball) on the foot spot so that the back of the rack (the base of the triangle) is parallel with the foot rail of the table.
The balls should be snug in the rack — they should all be touching each other. This is called “a tight rack.”
These are the general rules for racking, but specific games will have specific rules.
In a rotation game — a game where you must strike the lowest-numbered ball first — you must place the number 1 ball (solid yellow) in the apex of the rack. In other games, unless stated by the players in advance, it's not necessary to rack the balls in any order. In a game like eight ball, the number 1 ball is usually placed in the apex, but that's just traditional.
Make sure you refer to the rules of the game that you're playing to find out if you have to rack the balls in any specific way. For example, in nine ball, you must rack the 9 ball in the center of the rack.
Don't be surprised as a beginner if your break shots are weak. It takes a little practice to get it down. You may find the cue slips through your fingers or maybe you'll hold onto the cue but you miss the cue ball. Maybe you hit the cue ball and it taps the racked balls and they go absolutely nowhere. These things can happen. But don't worry, with lots of practice you'll be able to break with the best of 'em.
A cue ball has been measured to move from 0 to 20 miles per hour in just a fraction of a second after it is hit with a cue.
In most games, if the cue ball leaves the kitchen, the game has commenced. Each game has different breaking rules, but, in general, if your cue ball leaves the kitchen and doesn't strike the rack, it is a foul and your opponent can break. Also in some games, four balls must make contact with the cushions or the break is considered a foul and your opponent can break.