There are three big body movements that should power your serve.
The first two have already been discussed:
1. leg push off
2. coil/uncoil of hips and shoulders
But in order to launch yourself up and at the ball and drive yourself into the court without spinning around and kicking your right leg off to the side, you will have to incorporate more:
3. cartwheel/bow shape/reversing the bow shape.
In this, you have to leave your tossing arm up straight longer to get a steeper shoulder angle in your serve:
Notice that as your upper body tips back to form the bow shape, you have to let your hip go forward to counterbalance this upper body lean:
Tennis Lesson: Serve Tips: Lead with the Hip http://www.youtube.com/watch?v=HgeYmEScfgQ
This clip of Soderling serving dramatically shows this:
Robin Söderling serve slowmotion http://www.youtube.com/watch?v=a56pvP1i6x8
The timing of when to form the bow shape for those with a platform stance is to do this fairly late - after you've finished most of the shoulder turn and knee bend - just before you get into your trophy position:
By getting pretty low with your knee bend, it is easier to maintain your balance as you form a bow shape, as Sampras does in pics 8 -9 above.
The other key is to have a VERTICAL rather than HORIZONTAL shoulder swing - the shoulders should rotate like in the video below:
Preventing Rotator Cuff Injury http://www.youtube.com/watch?v=lTRvxaBMh8s
[It is not only good to prevent shoulder injury, but throwing your shoulders up and over vertically will launch you "up the mountain" and into the court.
On the other hand rotating your shoulders horizontally will cause your whole body to swing too much - with your right leg having to swing out to the right to counterbalance this horizontal upper body swing swing.]
And yes, serving is really like throwing a ball up at the roof of a domed stadium.
"Up the Mountain" excerpt form Serve Doctor presents: M.P.H. http://www.youtube.com/watch?v=WlPVdppfYGs