How much can a player move or step in the process of serving: stepping as long as not crossing the base line? Jumping? "Volleyball" serve?
According to the International Tennis Federation, once the serve motion has started, the server is allowed to make small foot adjustments, but cannot take a step. If the server's feet come off the ground during the serve, that is ok. If the server decides to catch the ball and try again, that is ok as well.
Relevant info pulled out:
16. The Service
Immediately before starting the service motion, the server shall stand at rest with both feet behind (i.e. further from the net than) the baseline and within the imaginary extensions of the centre mark and the sideline.
The server shall then release the ball by hand in any direction and hit the ball with the racket before the ball hits the ground. The service motion is completed at the moment that the player’s racket hits or misses the ball. A player who is able to use only one arm may use the racket for the release of the ball.
18. Foot Fault
During the service motion, the server shall not:
a. Change position by walking or running, although slight movements of the feet are permitted; or
b. Touch the baseline or the court with either foot; or
c. Touch the area outside the imaginary extension of the sideline with either foot; or
d. Touch the imaginary extension of the centre mark with either foot.
Case 2: Is the server allowed to have one or both feet off the ground?
19. Service Fault
Case 1: After tossing a ball to serve, the server decides not to hit it and catches it instead. Is this a fault?
Decision: No. A player, who tosses the ball and then decides not to hit it, is allowed to catch the ball with the hand or the racket, or to let the ball bounce.