At the start of the motion, Roger's racket and racket arm point basically straight ahead at the net. His tossing arm also points straight ahead with the ball resting roughly on the throat of the racket. Note also the angle of his shoulders. In the ad court they are a little bit shy of perpendicular to the net. In the deuce court they are open an increment further. This difference in the shoulder angle is analogous to the small differences in the angle of his front foot. Don't worry too much about the position down to the inch.
Also, don't be fooled by the personal physical rituals players use at the start of the serve: Roger's rocking motion, etc. The players are all a little different. What matters is what happens when they start the motion. Every player eventually develops his own rituals. Rather than model Roger's rituals, it's better to model the elements in his stance first. To do this, position your feet, torso and racket at Federer's angles as described above, and just stand straight up and down with your weight more or less equally distributed between your feet. Your arm and racket should point more or less straight ahead. You can also start with less left-to-right offset between the front and rear foot. I like to position players with both feet paralel to the baseline with the heels lined up and the shoulders fully square to the net and let them evolve their stance from there. As you get comfortable with these elements, you'll develop a unique physical ritual of your own.
I love Roger Federer's wind-up because, other than Mark Philippoussis, it's the longest and most circular of any of the top players. True, the abbreviated backswing is the overwhelmingly trendy motion. Andy Roddick set off that craze, which has mesmerized and infatuated players, coaches and commentators. We saw in our Roddick articles that, at least for Andy, there probably is some technical advantage to it. As Rick Macci was the first to point out, it allows him--or forces him--to move in and out of the racket drop faster than any other player. And that's a beautiful and fearsome thing. The question is whether it is remotely realistic for the average player. And I have an answer: No. So far, Andy is the only player I've ever filmed that has made it work.
The point of the wind-up is to position the racket at the full drop position so it can then travel upward to the ball on the right path and with the most speed. If the wind-up doesn't accomplish that, you're probably better off starting the motion with the racket already dropped behind you. Unfortunately this is exactly the case for many players who try to copy Roddick. They fail to make the basic drop position.
It's absurd. A player decides that by modeling Andy's backswing he can get more racket head speed and it ends up creating the exact opposite effect. Trying to add an esoteric advanced element players sometimes destroy the more basic element they think they are trying to enhance.
Abbreviated windups are fine so long as you can rotate your arm backwards in the shoulder joint to get to the racket drop like Andy. The problem is that very, very few players actually can.
Watch Roger's arm and racket in the wind-up. Rather than starting immediately upward like Andy, his arm and racket drop downward at the start of the motion, pointing directly down at the court. This is similar to Sampras who also drops his arm and racket downward so they point at the court. At this point in the motion, however, Sampras begins to abbreviate the backswsing, bending his elbow and starting to raise the racket from the shoulder.