1) Make sure you have all your equipment ready: racquets, wristbands, tennis shoes, spare socks, spare shirt + shorts, water, Gatorade, a dry towel, a wet towel (for wiping sweat off your hands), sweat pants and a sweatshirt / warm up clothes, a hat, sunscreen. In very hot conditions, bring a cooler with an ice pack. Placing the ice back behind your neck during changeovers is the fastest way to cool down.
2) Eat a good meal with lean protein like Chicken, some vegetables, make sure you have vitamins, be well hydrated throughout the day prior to the match. Bring bananas to eat during your match. You should have one after the first set to stay energized.
3) Think about your gameplan, and talk it over with your coach/friend/parent.
4) Check in at the tournament well before your match – maybe an hour before. Get a sense for whether or not your match will be on time, and let them know you’re there so you won’t lose if you show up late.
5) 10-20 minutes before your match is about to go on, get warmed up. The on-court 5 minutes they give you before the game is not enough. If there are courts to get warmed up on, then great. If not, then no problem. I like to jog outside, maybe around the parking lot. I do some skips, circles with my shoulders, stretch very lightly my wrists and legs, do shadows with my racquet, or hit some volleys against a wall to get my hand eye coordination warmed up. Skipping a little bit is good too for general coordination warmup. You just want to have your muscles feeling warm and your ligaments loose. You don’t want to be exhausted. A light sweat is ok as long as you know that your match will be on time. The last thing you want is to get warmed up, then have your sweat cool down, and your muscles to be stiff and cold by the time you get on the court. So you need to time your pre-warmup carefully and do it close to the match.
6) The pre-match warmup is not the time for any technical tips from the coach. It’s too late anyway, so all you want to do is be positive to get the player feeling confident. I typically like to do my pre-match warmup ritual on my own. I do the same thing each time, and the alone-time gives me time to get comfortable. Once I get on the court I’m going to be dealing with everything alone, so it’s good to collect your thoughts.
7) Check out the conditions of the courts. What side is the sun on? You don’t want the sun in your eyes when you are warming up your serve. Is it windy? Which side has the wind behind you? You probably want the wind behind you at the start of the match when you’re a bit nervous and not swinging through the ball. Are there shadows covering part of the court? Can you take advantage by hitting the ball there and making your opponent have to deal with it?