Accidental Spin
What do I mean by "accidental spin"? Some players will think they are hitting center ball, but they are not. There are two basic reasons for this:
1) Visually, they are not accurately seeing the center. I recommend practicing a center ball hit using a striped ball. Set the ball so the number is parallel to the felt. Aim to strike directly on the number. Stroke very gently, not even enough for the ball to travel more than a few inches. Then look at the ball to see the chalk mark that your cue tip made on it. Is it dead center on the number? Congratulations! You hit center ball. Now, repeat this exercise until you are consistent.
2) There may be a mechanical problem in your stroke. There may be a hitch, or you may be standing up as you shoot. A crooked stroke can be corrected by focusing first on your stroking arm (the back, or right if you are shooting right-handed). Your shoulder and upper arm should be as level and parallel to the floor as possible. Your grip should be loose. If the cue is touching your palm, you are holding it too tightly. Your wrist should be straight and the cue cradled between your curled fingers and thumb. There should be no shoulder nor upper arm movement. Your hand and lower arm should swing like a pendulum as a unit. Always try to keep your cue as level as possible. Any time you raise the butt of your cue, you are applying masse (curve). This is okay as long as you understand what you are doing to the cue ball, and know how to adjust your aim accordingly. If the cue ball is against or close to a cushion, use a rail bridge and back it away from the cue ball, so that you can level your cue as much as possible.
Whether you use an open or closed bridge is purely personal preference, as long as you are forming a ridge through which the shaft slides smoothly and snugly. Practice the stroke, carefully observing these fundamentals before ever stepping to the cue ball (much the way golfers will take practice swings before stepping to the ball).
