(This is today's bit of advice from the book Safety Toolbox.)
Side spin (also known as English) occurs when the cue tip contacts the cue ball to the left or right side of the vertical line (12:00 to 6:00). The cue tip contact can range from a very small off-line of 1/8 to 1/4 tip away from true vertical) to contact points that are so far out (2.5-4 tips out from zero position) that the cue tip cannot make a firm contact. The result is a miscue with the cue skittering away and the cue ball reacting strangely.
Cue tip placement out from the vertical center determines amount of side spin. The closer the tip contact is to the vertical center, the lower the amount of side spin. The further away, the greater the spin. The most common adjustments are calculated in tip widths from the center (zero position): ¼ tip, ½ tip, ¾ tip, 1 tip, 1-1/2 tips, and 2 tips out from center. Intentional cue ball spin is useful in offensive and defensive situations.
It is when the spinning cue ball contacts the cushions that you see interesting results. The spinning cue ball comes into the cushion at one angle, but comes out of the cushion at a different angle because of the amount of side spin. The angle out from the cushion can be controlled with remarkable precision.
The clock system describes how to hit the cue ball. The most dramatic reaction off a cushion is when the cue ball is spinning from a 3:00 or 9:00 hit and at slow speeds. Some cue ball activity can be quite surprising. These exercises allow you to achieve results intentionally, not by accident. The cue ball graphic shows one tip out from the zero position.
The secret of great ball runs is precision cue ball action. Mastering side spin exercises make many seemingly impossible shots – possible. Although the majority of shots use the trustworthy vertical 12:00 to 6:00 line, side spin gives you additional options.
When performing the exercises, pay close attention to the results and make adjustments accordingly. Use visual feedback to make rapid improvements. Experiment around and figure out what works.