Now, we all know a good shot fake when we see it. A shot fake is meant to draw a defender closer, in order for you to drive around him. If you shot fake too quickly, then he can't see it and react to it. So slow it down. Think slow shot fake, but quick drive.
As you develop your shot fake, don't try to do too much. Less is more, and simple is best. Just take your normal shot motion, and stop short before the ball gets to your nose. Don't raise up and come out of your triple attack position or you'll lose the ability to be explosive. You might find it helpful to get in front of a mirror and see if you can sell yourself with your own shot fake.
Now, the shot fake should go no higher than your nose for two reasons. First, you don't want to block your vision of the goal or the rest of the players. Second, a high shot fake slows down your drive. I don't care how quick your feet are. In order to drive, you must put the ball on the ground. So you can't begin to go by the defender until the ball has moved from the top of your shot fake, back down to hip level, and then to the floor with your first step. A high shot fake means the ball has to travel a long way and that takes a longer time. A shorter shot fake means shorter distance and shorter time. This is called "being quick with the ball" or "ball quick".