Technically, the most important part of the third shot drop is to use the exact same technique as your dink and visualize it as nothing more than a long dink. Working on dinks from the baseline is one of the best ways to visualize your own third shot drop.
Technically, the further back you are, the higher your drop shot can go. Try to visualize the ball falling into the kitchen. Lift it up and let it fall in the kitchen, trying to think of a nice, soft, high dink. Very small back swing, very small follow through. The simplest way to do your drop shots is to visualize them as long dinks. You should not skim the net, you should try to let the ball fall into the kitchen.
The other technique on third shot drops is more advanced. Roughly 25% of the professional players do it. The technique is to make your third shot drop look exactly the same as a drive. It’s a little harder to drop, but some players will wind up and smack a hard third or wind up and look like they’re going to kill it, but then do a drop shot.