Just want to provide tip here re:Reviving Serves.
Its winter time here. Stuck in my house with no money to play indoors. I want my serves back. I do a lot of shadowing strokes including serves (we have a high ceiling family room). After 2 months, it gave me muscle memory on how to execute them properly.
How the hell i got muscle memory? Simple. I covered the string bed with cut-out plastic, tape it back to back. It has drag which enabled my arm muscles to exert efforts at the ball impact zone of my strokes.
Its really addictive doing it.
I happened to drag my toe a lot. Now, its automatically jumping, just the way like Federer. I found that my legs' the culprit. The left leg must get all the body weight during the toss action. I'm a righty.