This is a great movement to use as a warm-up because it activates the nervous system without overly fatiguing the body. It also teaches you to jump with a weight in your hands, as with Olympic-style lifts.
The movement with the legs should be very fast and explosive. Use a powerful hip action.
The arm with the dumbbell should stay close to the body as it rises.
Remember, while you do pull with the arm, it's the movement created by your lower body that gets the dumbbell overhead.
Besides meaty arms, the pectorals are probably the best of the "showy" body parts. Somewhere in time (oddly enough at the same time as the rise of Arnold Schwarzenegger), the chest became the ultimate sign of manhood. Thick pecs give a three dimensional look to the upper body, and a well-defined chest makes your torso look like an old Roman soldier's breastplate.