http://www.youtube.com/watch?v=oSHTBGTeXq4
Why Do It:
The higher the hips, the less resistance you create with the back half of your body. This means it'll be easier for you to move through the water.
How to Do It:
1. Obviously, you'll think about this during any freestyle swim or set.
2. Focus your attention on your hips, and their connection with the surface of the water.
3. There will be a few options for you to get your hips a bit higher... lower the head,
tilt the pelvis, tighten the abs(Becken nach hinten kippen, ziehen in der Bauchdecke

), kick a bit more... the list goes on. It'll be up to you to determine which works best and which you can accomplish most consistently.
How to Do It Really Well (the Fine Points):
Make sure you're always showing some part of your hips or suit above the surface... at all times (during swimming). Don't allow your hips to drop back under and continue to focus on the muscles you'll be using to accomplish this.