I mean really turn, not just your shoulders. Really rotate the trunk as well because if your hips don't turn and your shoulders do, they will only unwind too quickly and pull you out of the upward motion you need. If the toss is correct, it will normally keep you turned throughout the shot. Overhead and around 11:30. You can adjust the number position according to your preferences, but 11:30 is optimal. I tend to turn my feet as well to keep everything inline as well. Now, I stand in the ready position when serving totally normally, but as I step up and turn my body, my feet pivot as well. (I platform serve. Bringing the feet together.) I stayed turned through the shot while still uncoiling hard and up into the ball. That is why the kick serve tends to hurt people's backs a little. You need to do lower back exercises to strengthen that area to avoid any problems......Get the feel of it. I say it is a feel shot and that will make more sense to you when you start hitting it just right. Your hand snapping up and around the back of the ball is the key thing you need to feel.......