Practice breaking a rack of balls many times in 8-ball, 9-ball, 10-ball, and One-Pocket to find a consistent spot where you scratch the least. Scratching at any time takes the advantage away from you and gives it to your opponent. When you have made a ball, evaluate the positioning of the remaining balls by walking around the table (things look differently from different rails). Pocket as many balls as you can, concentrating on balls on rails first and breaking up joined balls.
When you have a high-risk or low percentage shot, leave your opponent with either a difficult shot, or one or more balls located such that a run-out is unlikely, giving you another opportunity at the table. Avoid scratching or fouling.
Column 1 is the value of an object ball. Column 2 is the value of two object balls.
8 BALL 6.7% 13.4%
9 BALL 11.0% 22.0%
10 BALL 10.0% 20.0%
1 POCKET 12.5% 25.0%
Every shot is important. Make sure a ball is pocketed or reaches a rail (any object ball or the cue ball).