Ray Bechard talks in this video about important keys to a good serving routine.

1. It should be repeatable.
2. Simple is better than complex.
3. Toss should have minimal motion.
4. The routine should have a mental component to it. For example, a deep breath or a phrase that you repeat before every serve.

Finally, Bechard notes that it helps the server if the coach is sending positive energy from the bench with good body language and some words of encouragement.