Every shot has its “ideal” contact point, so remember the acronym 'PAS', which stands for: Path, Angle and Speed.
1. Path: Path is the way the racket travels forward after the backswing. With a classic forehand or backhand for example, the path starts low, then forward through the ball, and finally ends high above the shoulder. On a slice it tends to be the opposite in an up-to-down trajectory. Some shots can also have a left to right trajectory or vice versa.
2. Angle: Angle refers to how the face of the racket is positioned when making contact with the ball. In general terms, angle can be understood vertically, horizontally and laterally. This factor will obviously dictate ball direction heavily.
3. Speed: Speed relates to how fast the racket travels through the contact point. On a slice shot for example, slower speed with a slightly more opened angle is the difference between a regular slice and a drop shot.
In summary, the combination of 'PAS' will set the direction, height, length, spin and speed of the ball. The secret here is to understand how these elements together dictate the kind of shot you will generate.