Sex

I'm writing a sex scene. This is among the most difficult of writing objectives, because if you fall short of the mark, readers become intensely dissatisfied, and are more likely to stop reading than at any other part. Sex is such an important part of our human experience, that in reproducing it, we are bound by several things.

Accuracy
A sex scene must not be unreasonable or beyond expectations. It must fit with the character as well as with his/her partner. It must feel natural, as though it were actually happening. It must fulfill both sides of the gender role, and must be a situation that can (or has) actually happen.

Allure
A sex scene must appeal to both genders. No one wants to read a sexual encounter that appeals to purely one gender. A guy must read the scene and get an erection. A girl must read the scene and become wet. The only acceptable byproduct of a well-written sex scene is a reader who sets the book down and looks around, wondering, "can anyone tell that I'm supremely turned on right now? Who's that guy/girl? Why do my pants feel so tight? Why is my skin tingling?"
and then reread the passage, thrilling and squirming at every paragraph, gulping and cringing at the need to penetrate/be penetrated.

Amazement
Readers need to stop halfway through, wondering how it's possible the writer knows so much about what he/she is thinking. A reader should be almost shocked at the closeness of the scene, nearly stupefied that the writer is so deeply connected with humanity to understand so completely what's going on on both sides of the slish contact between two people that the writer must be schizophrenic, or at least godlike in ability to round out the connection.

This is what I must accomplish. A weak sex scene is enough to destroy an entire book. It can be a make/break scenario within which, a reader's life can be changed merely through the emotional impact passed along by a few choice words.

How to make that connection? How to accomplish that accuracy, that allure, that amazement? Practice, practice, practice...