Eight Ball
Eight ball is the best known version of pool. The object of the game is to sink the eight ball after sinking all of the other balls assigned to you. One player will shoot for the solid colored balls and the other goes for the stripes. Typically, whoever sinks a ball first gets that kind of balls. When shooting the eight ball, you must state which pocket you are aiming for. If the eight ball goes into a different pocket -- or if you sink the cue ball while aiming for the eight ball -- you lose. If you sink the eight ball before clearing the table of your assigned balls, you also lose. However, if you sink the eight ball on the break, you automatically win.
Nine Ball
Nine ball only uses nine of the 15 balls during the course of the game. Whoever sinks the nine ball first wins. The trick to nine ball is that the player must make contact with the lowest numbered ball first when taking a shot. For example, if the three ball is the lowest numbered ball on the table, the player can either try to shoot the three ball in or use it to hit another ball in. If the player uses the three ball -- or the lowest numbered ball on the table -- to hit the nine ball in, that player wins. If only the nine ball remains on the table, the first person to sink it wins.
Last Pocket
Last pocket is a variation on eight ball except it requires a little more focus, strategy and skill. Like eight ball, both players must sink all of their designated balls first. Whatever pocket your last ball falls into, that's where the eight ball needs to go. For example, if you sank your last solid ball into the right corner pocket, you must sink the eight ball there as well. If your opponent sinks her last ball into the left corner pocket, she must place the eight ball there. If either player sinks the eight ball in the wrong pocket, they lose.
General Rules
General rules can vary between players, so double-check them with your opponent before playing. For example, when you scratch in some versions -- or shoot the cue-ball into a pocket -- your opponent must place the cue-ball back behind the breaking line. In other versions, your opponent would have "ball in hand," meaning she can place the cue-ball anywhere on the table. In call-shot games, the player must state ahead of time which pocket her ball is going into. If the ball doesn't wind up in that pocket, her turn is over. In "slop" versions, players do not need to call their shots ahead of time.