I believe, the concept “From the beginning to the finish” works on the serve, as well as on any other shots and strokes. To define “The Beginning” of the serve swing I refer to the good, old “Trophy Position.” One important point here is to be flat like a “sticker” on the wall, meaning to have the shoulders, dominant arm, and racquet flat on the wall behind. At indoor clubs tarps are perfect for that. With the entire body touching the tarp: from heels all the way to elbow and knuckles of the dominant hand, the feed back of being in the right position is strong and bold. For some players this pose is easy, for some it is very challenging, but in any case, doing it at the early stages of acquiring the overhead swing motion is the most helpful, in my opinion. Racquet, held with continental grip, should be flat on the tarp as well, right above the head, with the entire frame touching the tarp. That would be “The Beginning of the Swing.”
To get more comfortable to be in this “trophy position” I use three steps toss practice.
I suggest players to toss and catch the ball with non-dominant hand 20 times or so, just standing in that position with the dominant arm doing nothing, but just being there. For some players it turns into upper body work out.
Tossing is a trick of its own. I suggest to keep the palm under the ball and hold the ball in the fingers. Good way of learning to hold the ball this way is to hold two balls in the non-dominant hand first and even toss the one while keeping the other. This way “lifting” of the ball is getting accomplished instead of “throwing” the ball upwards. After using two balls for tossing for some time, getting rid of the second ball leaves the only ball to stay in the fingers exactly as needed: the ball is held by the thumb, index finger, and middle finger, leaving ring finger and pinky finger comfortably flexed, but not squeezed towards the heel of the palm.
I also like to suggest to do a small “pumping” motion with the tossing arm: keeping it almost completely extended, but not locked straight in the elbow joint, lifting it to the waist level or slightly above, then dropping it to the non-dominant hip, knuckles down, and sort of bouncing of the hip back up, this time all the way up, yet not the absolutely vertical position. During this “pumping” the ball is getting let go around shoulder level, basically being lifted by the vertically moving “platform” of the palm.
After 20–30 “Sticker Tosses” and catches, I suggest players to test themselves and do 20–30 “Seam Line Tosses” and catches. First time I have seen this tossing practice was at the class ran by Brian McNamara, well known coach and player developer in Chicago Metro area. The way that works is to do the same tossing practice standing this time perpendicular to the tarp about 1′ or 30–40 cm to the side of the tarp’s seam line at the extended arm distance away from the tarp. Seam line of the tarp is used now as a 3D guide for the toss: the ball should be going upward along the line, right-left wise, close to it, forward-backwards wise, and high enough to have room for the extended dominant arm and racquet to comfortably go through it down the road. I strongly urge not to “trap” the ball to the tarp, as unfortunately so often done with the beginners. This trapping exercise, with the honestly good intentions, stimulates “Fly Swatter” habit that ruins the flow and feeds muscle memory with injury prone abrupt motion. I do not like it, but that’s just my opinion.
Testing part of the “Seam Line Tosses” is to remain “Sticker Flat” without any guiding behind. Be aware of the two most typical things that usually go loose: a) the racquet face opening upwards to the sky or ceiling and b) dominant elbow moves forward in front of the chest.
Third step is tossing the ball standing on the court. I still suggest to use the court lines and relate to them to position the body somewhat perpendicular and sideways to the net. Good way to do it is to be at the service line instead of the base line and do 20–30 standing free tosses and catches remaining in the sticker position and having accurate toss as much as possible. Center line and side lines can be used as a guides for tossing arm to along those lines forward. Typical error to be aware of here is to not “J” the tossing motion starting it with the circular motion around the waist.
For the final step I also suggest to serve from the service line or even closer to the net positions. I want to eliminate “aiming” and possibility to “miss”. I suggest players to serve “straight ahead and far” using base line as a depth mark for feed backs, but not the target. I’ll explain this in just a minute.
There is also “The Beginning of the Serve” position with hands together down in front of the body. I recommend to have the ball somewhat comfortably placed in the triangle opening of the modern racquets’ throats. This way the space between the hands is the most anatomically relaxed: hands are just a little less than shoulder distance apart, as opposed to being farther than shoulders distance apart when the ball is placed against the strings or being to close together, when the ball is placed with non-dominant hand under the racquet shaft, usually right above the handle. additionally, and I think it is super important for swing motion, when the ball placed into the “V” shape opening of the modern racquets’ throats, two fingers: the ring finger and pinky finger, that are free from holding the ball can be used to support the racquet right around the middle of it, thus allowing dominant hand to be absolutely relaxed prior to the beginning of the tossing and service motions.
After getting good at doing all three tossing steps with the racquet at the “flat sticker” position or “Beginning of the Swing” position, it is important, to progress to the next three steps of tossing practice. Same three steps of tossing practice needs to be done with the Beginning of the Serve to Beginning of the Swing transition of the dominant arm with toss motion being timed at the same time when racquet starts transition.
The rhythm of the serve is the the count of “three”: “Beginning-Beginning and Finish” with toss simultaneously happening at the first count, of course, when both arms dropping downwards and going back upwards: non-dominant arm tossing the ball with the best possible accuracy and dominant arm finding the “sticker flat” “Beginning of the Swing” position for a momentary aiming delay.
“The Finish” of the serve swing is on the opposite side of the body with dominant thumb pointing backwards and touching the non dominant side pocket of the shorts or just the hip. Touching actually is not necessary at all, but using it at the beginning gives the “concrete” destination for the swing to go to. And it is absolutely crucial, in my opinion, so that the swing is free from “player’s own interfering instructions.” If the racquet gets released from the hand at that point and dominant palm gets open, it would be facing the hip. This allows pronation trick to happen effortlessly and without messing up the swing flow. When players use continental grip for this specific “Finish” and serve from very close to the net without any particular target on the opposite side, ball starts going flatter, heavier, and straighter pretty soon. The trust of swing with continental grip is getting developed very effectively. Serving this way from the service line and strait ahead to the baseline imitates serving from the base line to the service line at 100%.
One more reason to put more effort into practicing the toss and racquet setting into “The Beginning of the Swing” position is that to be comfortable, accurate, and consistent the entire serve depends on the three things: a) the ball needs to be tossed accurately in the comfortable area, b) racquet needs to be in a rational “ready to be thrown” position or pose that is a combo of your body and racquet itself, and c) legs need to be in the grounded, not leaning forward balance and athletically engaged with knees bent to generate push off the court, jumping eventually, and the torque from hips and torso.