Always begin with a "dynamic" warm up before the match with a little jogging to raise your heart rate and get your legs moving. Before even taking the court, execute at least a few backhand, forehand and service motions to work your core, back and arm. In your on court warmup, you can hit the first couple of balls slow, but quickly get up to the hitting speed you expect to use during the match. Hit some volleys, and take enough serves and a couple of overheads, just like you see the pros do when they do their on court warm up. Notice if he has any obvious strengths or weaknesses, and if he seems to move well on the court.
If you can arrive early and there is a hitting partner and an open court, by all means spend some time warming up your match with groundstrokes, volleys and serves. If there is no hitting partner you can still run a quick agility drill consisting of running down the deuce sideline, side skipping cross court just in front of the net, running backwards up the ad sideline, and side skipping across the baseline.
If there is no one there, but there is a backboard, a few minutes hitting groundstrokes, volleys and serves against the backboard will also help get you match ready.
