I would generaly agree with what JKogas has said on this topic. I would also add that hitting "through" the target is vital rather than "stopping" the strike on first impact. Also, learn to chain the muscles in throwing the technique. For example in a hook punch, the power comes firstly from the foot positioning, then from the knees, then the lower back and so on. The torque from all these muscle groups should be unloaded virtualy as one, like a spring uncoiling as the arm whips across and though the target.

Mr V