There are a lot of things that can contribute to an effective second serve. Things such as 1. Keep your head still; 2. Relaxed arm; 3. Shoulder rotation; 4. toss the ball a little over your head for good kick; ...... What is the most important element? I think it is a consistent toss. Without a good toss, even the best service motion won't get you a good serve. Thus if you are not happy with the toss, you should stop the swing, catch the ball and do it again. What do you guys think?