It's rather simple once you understood it. You just need to weigh lighter than the force you could produce with your movements.
ATP Pros are skinny and strong. They don't do anything special other than running and hitting very hard and the thrust of their actions lift up their lightweight bodies.
For this reason WTA pros don't go airborn as much as the ATP.
Well, Serena and Sharapova can run up and smash a FH winner with their feet off the ground though.
Fat or out of shape guys, no matter how technical, won't go off the ground much either.
How is this a 5 star thread whereas other much worthy threads got 3? :confused