Be a good detective! Next time you play someone watch carefully during the warmup. You can find a lot out about a player by how they warmup. Are they hitting any backhand ceiling balls?
No? Well probably they cannot execute that very well. (Okay outdoor players-please resist the temptation to bust my chops here). Do they practice serves? No? They might not be too accurate serving!
Practicing lots of pinches and splats? Or just the opposite? That might give you a clue of where to position yourself.
Are they practicing any down the lines? No? You might be able to give up the down the line to cover pinches and cross courts!
What is their temperment? All fired up with the game face on? You might be able to laugh and joke around to diffuse the feisty opponent. Opposite? All laid back and at peace with themselves? hmmmmm–maybe something would break their concentration such as taking your legal ten seconds to receive serve. Are they looking back before practicing drive serves? Might be able to poach a second serve by taking your allotted time.
What is their backhand or forehand like? Spot any “wavy gravy” or excess motion? That extra motion might be able to be attacked.
These little things could be the one or two point difference in the tiebreaker!