14.

The key point to the best hand technique lies in the motion of the elbow. The key point to the best kick technique lies in the motion of the knee.

The key point is the principle of mind. It is what you are supposed to intend for best movement of your body, i.e. the exact way of using your mind. You cannot master each technique without understanding of those key points in your basic training. Your training should be wise in that manner.