high lights of the article are: it's a step by step way to improve your strokes
Step 1: Identify a technically “perfect” stroke on YouTube.We’ll call this the “control” video. It should be of a pro hitting in slow motion with a good view of the player from head to foot. This video of Thomas Berdych’s 2 hand backhand is perfect:
go to the site for this video
Step 2: Film 3-5 of your sessions on a ball machine.Set up a camera on the baseline. It doesn’t need to be my VolleyCam, or anything expensive, but high definition will be a big help. Hit a few hundred balls at a time and return home to compare your stroke to your “control” video (in my case, Berdych hitting backhands). Identify one thing to work on during your next session (ie, shoulder turn, extension of left hand into court, etc.). Keep it simple, and focused: you can’t learn it all in one session. With each session, compare videos and “check off” each element (shoulders, knee bend, footwork) until you have a fundamentally solid and repeatable stroke.
You have to hit about 10,000 tennis balls to learn something new. With video analysis, I’ve cut that number in half.