Developing Drop Shots
You can hit a drop shot with almost pure underspin, a combination of side and under spin or in rare instances with a combination of under and outside spin. If your opponent plays way behind the baseline, is inattentive, does not move forward well, or has trouble with low balls, hit dropshots. If you mix in deep slice approaches, even better.
If you really get a feel for the spin you can learn to drop shots that bounce back over the net to your side!
I haven't talked much about grips, and I don't believe in absolutes, but you need a trigger finger if you are going to have good touch. If you are trying to hit a forehand drop shot that bounces backwards you probably want something close to a 1 -1 or an eastern backhand grip.