Take a trick you already do that has a sleight in it that you want to improve. Now do the following.
Perform the trick in front of a mirror or a camcorder. If the sleight or any other part of the trick "looks funny," then work on it until it doesn't look funny any more.
Here's a hint. Let's take a simple sleight that everyone who does coin work or cups and balls work must know how to do -- a false transfer. Forget all of the material you have read in Bobo or anything else. Just pick up the coin or ball and place it into your other hand. Actually put it there, don't try the sleight yet. Make sure that when you place the object into your hand, you close your fingers around it, so you know how much room the object actually takes up.
Practice this until you know how your hands actually move and how they feel when you do the real placement of the object.
Now, practice the false transfer. Pick the object up and pretend to place it into your other hand, but retain it instead of placing it. Make sure that both hands look exactly like they did when you performed the real placement. Think of the weight of the object in the hand where you supposedly placed it. Make room for it.
Now practice that until it becomes boring. Then practice it until it becomes beautiful.
Bear in mind that if you are learning a sleight such as a false transfer, you must learn it IN CONTEXT, that is, you must plan where the hands go after the false transfer is made. Perhaps the hand that actually has retained the object now goes to pick up a wand or a cup. Then practice the move in that context.
Bill Palmer, MIMC