As Blackie Jones (my first coach) would ask of a student,”If there are two parts to the serve, being the toss and the swing, do you think it is better to swing at the toss, or toss into the swing?”
And as his lessons and demonstrations proceeded, we were schooled in the tempo, the technique, and the benefits for a toss that was low without being overly low, and this produced a motion that was rhythmic and flowing.
Consider servers with the overly high tosses – Del Potro, Sharapova, Safina, Berdych, Soderling – they all serve well but with an overly high toss that requires the slightest pause or hitch as the ball descends. And hopefully these servers are not playing in the wind.
Now contrast with servers who lower their tosses, essentially tossing the ball in the way of the swing – Federer, Serena, Dolgopolov, Kirilenko and remember Roscoe Tanner – they use a lower toss that unlocks a flowing rhythm.
Try this at dusk when you can see, but not perfectly. Now rhythm will be the key, and that key will unlock a serve where you are truly “tossing into the swing.”