Potting balls is easier if you know the cut angle and where to the contact point is on the object ball.  Below are some cut angles and the accociated spot on the object ball (grey OB)... now it is just a matter of knowing what the cut angle is plus stroking, stance, hand, eye co-ordination... blah blah blah... this is of course if your are aiming through the middle of the cue ball.. putting left or right english will deflect the cue ball and miss your aim target on the object ball slightly to alot depending on kind of shaft you shoot with.

You can download the picture below in the download section.