The speed and spin you use as you hit a ball makes a difference.

Rail shots in particular are tricky. Realize that if you hit the object ball before the rail, the collision has a tendency to push the ball into the rail (collision induced throw) and it bounces off and misses the pocket. According to Jack Koehler in "The Science of Pocket Billiards", you usually get the best results hitting about a tenth of an inch away fron the ball. He also says for shallow angles to put a little outside spin to overcome the collision induced throw into the rail and the add inside spin for real steep angles to make the cue ball spin into the object ball off the rail. That advice is great if all you want to do is make the object ball. Getting the cue ball to go to a particular position for the next shot means you often can't use the optimum techniques to make the ball. Remember that you are going contrary to the best practice of making the ball when you are trying to get position. Often you will have to compensate and make a more precise shot to make the ball and get position.

Below shows where a natural roll without spin will usually send the cue ball on a rail shot. Putting draw (backspin) and or outside Englsih can pull the ball back. A lot of draw and english lke this can pull it back 3 diamonds as shown. Beware, sometimes this puts you in the side pocket for a scratch. Follow and inside English make the cue ball stay down at the far end of the table. It seems like this often results in scratching in the corner pocket so be careful.