How to write a sex scene

We all love a good sex scene when we read a book aye. But writing a sex scene isn't that simple. You need to captivate the reader and make him feel like he is watching a real life porn action. Hehehe. So if you are a writer, and planning to include some sex scenes in your new book (of course you must!), then this series of how to write a sex scene will be helpful to you. From Storytelling:

The first rule for any sex scene is that it has to contribute to the characterizations and the plot. In this case, we have two people in bed together for the first time. They've only known each other a few days but there's a lot of tension between them, sexual, personal, professional; she's got a secret he's determined to unearth because he sees her work as possibly damaging to his own. Sophie is unsure of herself in a lot of different ways, and at odds because she's wildly attracted to this guy and doesn't trust him.

This is the first full sexual encounter (although there's a very interesting assignation on a boat dock earlier), and right off Sophie's not having a good time. She's wondering how to tell him it's not working, and that maybe they should go watch television, when he figures that out for himself and takes steps -- without interrupting what he's doing.

Part One: Humor, Part Two: Lyricism, Part Three: Stream of Consciousness

(Thanks jenibabe)