Performing a double hit on the cue ball.
Shooting the cue ball off of the billiard table.
Performing a Push Shots.
Moving the cue ball or object balls with the butt of the cue or ones hand.
Illegal jump shots according to the general rules of pocket billiards.
When a player commits a scratch on the cue ball, the next shot must be taken from behind the head string, and shot up table past the head string in that direction. Generally, ball in hand is not allowed according to the 3 ball rules, but some folks do implement this at times. When implementing this type of rule, all participants must agree before play begins. Most experienced 3 ball players frown on the ball in hand implementation, as it effectively punishes the shooting player for the foul, but then rewards them immediately afterward, canceling each other out. When an object ball in struck from the table, it shall be re spotted on the foot spot. No foul is assessed, since this act automatically forces the player to take another shot. Essentially, any act that is self punishing through the requirement of forcing the shooting player to take another stroke, does not count as a three ball foul. Legal shots include caroms, kicks, kisses, combinations, banks, and proper jump shots.
Three ball is commonly played for money, with players typically betting a $1 dollar to $5 dollars ante per game. The game of 3 ball is played frequently in San Fransisco California as a tournament game, but is also popular in other locales.
There isnt much to 3 Ball rules, but it can be a fun game when played with someone of equal skill.