All serves are different, aren't they?

Yes, the cosmetics (form) of serve differ from player to player, but most top serves share a range of common technical 'points' or 'moments' throughout the action (function).

Let's look at the preparation phase (set up > backswing and ball placement > pre-throw position) demonstrated here by Beth Grey.

Set-up 

  • Relaxed continental grip
  • Semi-closed stance - front foot towards net post, back foot parallel to baseline
  • 'Palm-in' racket 'side-on

Backswing and ball placement (toss)

  • Both arms down together before separating
  • Ball placement arm goes up earlier than racket arm
  • Ball is released at eye level
  • Knees bend as ball goes 'up'
  • Foot up (if) after ball toss and before load position

Pre-throw position (often a moment in time with racket arm moving rather than a still/fixed position)

  • Elbow is stable at 90 degrees (elbow to trunk)
  • Elbow is stable at 90 degrees (elbow to hand)
  • Pre- throw position when ball is at the apex
  • Slight tilt from front shoulder, back shoulder and back elbow
  • Palm of hand facing side fencing (palm out)
  • Both hips facing side fencing
  • Knees at most flexed in pre-throw position
  • Hip dipped slightly into the court
  • Eyes and head are focused on impact area