While you should vary your spin serves to all parts of the table – at least until you find out what gives your opponent trouble and what doesn’t – there are certain spin serves that are generally more effective when done to specific parts of the table.
The main principle to remember is that, in general, opponents will have more trouble returning a serve that spins away from them than one that spins into them. For example, when a righty serves a forehand pendulum serve to another righty (so that the ball breaks to the server’s right, the receiver’s left), if the ball is served to the wide backhand, the ball spins away from the receiver, and is usually harder to receive than the same serve to the forehand, where it breaks into the receiver. Similarly, a backhand or tomahawk serve to the forehand is generally more difficult to receive than one to the backhand, since it also breaks away from the receiver (to the server’s left, the receiver’s right). There are three reasons for this.