Hey, here are some tips!
What is important first is to be eating healthy. 2 things I concentrate on eating either before a practice or after is plenty of fruit (bananas - oranges), along with plenty of water, this flushes and cleans your system.
Another thing you should try, and some may disagree, but keep your warm up prior to practice limited and short. Do some stretching, but the practice alone will increase your flexibility. Stretching breaks down and inflames the muscles to a point. Practicing does the same thing at much more accelerated pace. When your practice is done, you should then complete a somewhat aggressive stretching routine. Why? Because your muscles are ready for it. Additionally, make sure you wear some type of sweats to keep your legs and upper body warm. Yes, it looks nice shakin your butt in those skimpy shorts for the guys, but take care of yourself.
And finally, if you are sore, take some Asprin or Aleve (with adult supervision). This cures the pain from the inside working out, which is better than ice, which works from the outside going in.
As far as the approach.. Look ahead for the take off spot where you would like to begin your elevation. Practice good techniques to get to it. Right now, focus on the combination of bending your knees (for height) and the positioning of your arms (kind of like a baseball picture winding up). Once you get to that spot, plant your feet, elevate, and begin arm movement to then strike the ball.
Let me know if this helps!
See ya on the court!