Looks pretty good all in all. I'll give you a few tips. I am not a certified instructor so take it or leave it.
1. You get a good front arm extension, but the loop on the racket arm and the drop of the front arm/shoulder don't seem to be in sync. Try thinking shoulder over shoulder where the front shoulder is higher than back when you front arm is fully extended. Then, the front shoulder pulls down and the back shoulder pushes up as you go up into contact.
2. Related to tip 1, you can get the feel of how the front and back sides work together by taking a few shadow strokes. pause in trophy position where front arm is fully extend, front shoulder is higher than back shoulder and racket tip is pointed toward sky. Now, work you hands together, the front hand will come down and stop at your chest (hand can touch chest around sternum), back hand will go thru loop and reach up into contact. Your racket hand should reach contact point at same time as you front hand reaches chest. The shoulder over shoulder action is integrated into this.
3. Last thing, hold your balance better. Sometimes you kind of fall into the contact. It is better to keep your weight back or slightly on front foot. You want your weight loaded into your legs so you can push up and in rather than fall in and drag the racket thru contact. Watch Federer, he doesn't poke the front hip out like a lot advocate. Rather his knees are balanced with a slight load to the front leg. You can still toss 1 to 1.5 feet in front of the body with weight balanced and still spring up and forward from legs.
Hope I have not ruined your serve if you chose to try any of this.
Last edited by TennisCJC; 01-22-2013 at 05:52 AM.