Forget all the sales talk and adverts on this video, but just watch the shape of the stroke to see how exactly the magic word "pronation" works on the service action.

Note how the racket is almost edge ways on as it approaches the ball - then squares off when hitting, and then takes a path across the ball to an almost 2 o'clock follow-through.

What is not expained is that it is essential to have a continental grip, otherwise forget it.

The idea is great and will give you that all so important spin on the ball - which of course will lead to greater control and then to more power.

Remember this is a second serve which is important to learn with the extra spin that you see here.

And below you can see the pronation of Andy Roddick on his first serve - just remember its a different angle from the video
But look where the racket has swung out to.