During the pre-match warm-up, I will hit several groundtrokes by hitting the ball way out in front of me, more so than I would in the match. Really helps me get off to a good start on my groundies.
Sometimes in warm up, I will pactice some serves standing about one foot inside the baseline and try to not fault. I think it forces me to get more arc or spin on the ball to get the ball in the serve box in a shorter distance. I think it helps to prevent long faults, my nemesis, when doing proper serves.