The week before the tournament, try to get a lot of practice in, playing singles/doubles, depending on the tournament. Try to eat healthier foods during the week. You do not want to risk getting sick. On the day of the tournament, wake up earlier than you usually would and do a few exercises, e.g. skipping with a rope, sprints, jogging Make sure to also stretch a lot so that you don’t pull a muscle.
Make sure you eat a healthy breakfast but try not to eat anything too heavy. Try to eat a cereal, e.g. Corn/Bran Flakes, Weetabix. Make sure to arrive at the the least half an hour before the tournament starts to warm up your strokes. Also run a bit (like 3 rounds around the court) before you step on the court. When you face your first opponent, warm up your strokes and serves with them so that you can develop a profile of how they play and use that to your advantage. When warming up with your opponent look carefully and take notes such as; their backhand is not as strong as their forehand, therefore you can hit to the backhand side; or whether they have a good strong serve so you have to be on your feet for the return.