First, enter a bar, such as "The Green Bottle" in the Ganton area of Los Santos. Find a pool table and wager whatever desired. If you lose the game, just use the cue stick to hit the person who just took your money to death. Then, pick the money he drops, which may be slightly more than your bet. Additionally, when you walk in the bar, either play a game of pool or just kill the man standing there and take his pool stick. X up with the pool table and start pressing B. The pool balls should move.