Ideally the ball that is coming to you should not be too low and will also have a little bit of pace on it - it is very difficult to hit a drop shot of a very slow moving ball. Disguise is vital. You ...
The drop shot—a slight gesture, really, better described as a “ploy” than a “stroke”—has often been maligned as cowardly. Roger Federer (ver. 1.2) once dismissed it as a “panic” shot.