Warming up with your opponent before a match is a perfect way to figure out their strengths and weaknesses. Before the match even begins you can start to dictate play and strategize a game plan.
The goal is to see what they can do with every kind of shot. If you start out with hitting at your opponents forehand, after 5 or 6 good balls in that general area, move on to the backhand, volley, etc… You’ll be able to tell what their strengths and weaknesses are and practice your directional control.