All the great shooters have great form. What is perfect form? It starts from the ground up, you have to be on balance, feet shoulder width apart for a stable base.
Now we move on to the hand, you want to be able to fit two fingers side by side between the ball and the palm of your hand, if the ball gets too close to the palm it gets really hard to control.
The next thing you want is an L-shape from your elbow to your shoulder and up to your hand [there are two right angles, at the elbow and wrist]. With your upper arm parallel to the floor, you should be able to put a ball between these three parts. That enables you to have great arc and soft touch.
The last thing is the follow-through, if you have nice, soft touch you have to have a great follow-through. You should be putting backspin on the ball so that it goes up soft. When you are finished your follow-through, your hand should be bent down like you're reaching in a cookie jar, imagine that you're putting your hand in the rim, right over the front of the rim.
Touch and Progression drills
With a partner, work on your mechanics and get a soft touch.
a) Flick the wrist - with shooting hand under the ball, forearm parallel to the floor, your other hand holding the forearm in place, flick the wrist, back and forth with partner. Get comfortable with flexibility in the wrist.
b) L-flick - from the L position [waiter position] with shooting hand under the ball, flick just the wrist, don't move the elbow (hold the shooting forearm in place with your other hand).
c) L-flick follow through - back up a bit, from the L position push the ball up like a real shot, flick the wrist at the end (don't hold the shooting arm with the other hand).
d) On your back - lying on the floor, make the L, flick the wrist, partner catches the ball and hands it back (the kids don't use a guide hand, when Nash demonstrates, he starts from the shot pocket, using a guide hand, brings the ball to the L or ready position, shoots, and catches the ball himself).