I play doubles, and I hold my racket up until my partner is in position and I am also ready. You'd be surprised how many try to serve while my partner is clearing a ball, putting it in her, walking to her position . . . .
I also have to guard against quick-serving partners. They miss a first serve, I clear it, and the next thing I know the serve is on its way while I still have a ball in my right hand. Now, I turn and face them until I have secured the ball and walked (sometimes backward toward the net!) into position.
There are some quick-serving players out there!
-- Random Error Generator, Version 4.0
-- Master Moonballer