The first step of the overhead is very similar to the pivot and shoulder turn for a forehand or backhand groundstroke. What you are trying to do is get your body sideways as soon as you realize that you’re getting an overhead and not a volley.
At 0:20 in the video above I am shadowing the overhead, and the very first thing I’m going to do is get my body sideways. The other thing that happens when I turn sideways is that I get my body into a position that looks very similar to the trophy pose on the serve. I have my racket and my hitting arm behind me in the “L position” with the racket pointed up at the sky. My tossing arm is extended up in the air, but unlike on the serve it is pointed at the oncoming tennis ball and not straight up. The reason I point at the ball is because it will help me to judge and time my shot later in the swing.
Let’s now take a look at a live hitting clip, at 1:00 in the video above. As soon as I realize that I am hitting an overhead, the very first thing I do is turn my body sideways. I then get my hitting arm and racket into the “L position” like I would on a serve, and I point my non-hitting hand at the tennis ball. Again, this position looks very similar to the trophy pose on the serve.
Let’s look at this step from the back. At 1:25, Adam is feeding the tennis ball to me and as soon as he hits a lob my body turns sideways, my racket and arm come into the “L position,” and I point at the ball for judgment and timing.