The players line up behind the deuce side baseline, having a tennis ball in their hands; the coach (F) is inside the service line, opposite side, ad court (see graphic below).
At coach’s command, the first player in line will hit a serve then moves up toward the service line where she’ll receive a short ball fed by the coach, then keeps going up towards the net and volley another ball fed by the coach.
She’ll then exit the court, get a new ball and jog around the court before positioning at the end of the line; all this time the next player will perform the same previous drill sequence.
Repeat the drill on the ad side too.
For large group of players, to avoid waiting in line, players should perform various exercises: jump rope, ladder drills, jumping jacks etc.