In the stance and throughout the approach the wrist and hand should remain in the loaded position: Thumb rotated more outside the fingers, placing the hand under the ball. Just after the thumb release break your wrist to the unloaded position.

 The thumb is now rotated more inside and forward of the fingers, placing the palm and fingers  to the side of the ball. The action is simple but takes time and practice to master.

Edited 19/07/11

Loaded 19/07/11