Always play the angles
To some extent, all sports are about angles. But in tennis, it’s particularly noticeable. Every time your opponent is setting up to hit a shot, you should imagine the widest points at which they could hit a shot that stays in the court. Then, set yourself up accordingly. Don’t bother trying to cover court space that your opponent can’t possibly reach with their shots. This is particularly important when you’re playing at the net. If your volley pulls your opponent out wide, you should move over as well, making it difficult for them to hit a passing shot and making it easy for you to direct the next volley in the opposite direction for a winner.
What's your strategy for playing the angles?