Originally Posted by Up&comer
Looks good. You look like you don't fully extend, though. Might just be that they are warmups.
Edit: you drop your left shoulder instead of going up with your right shoulder, which is why you hit or almost hit your racket on the ground every time.
I saw that as well. The push should come more off the back leg. Think that alone would add some MPHs to an already good service motion.