*cough*
Okay, this is a tiny bit embarrassing, but when I was in the middle of my first novel, I really needed a wild sex scene. It was an aspect of the story, illustrating the relationship the main character had with the love interest in contrast to the relationship he'd had with his fiancee. Lots of fighting and "making up".
I realized pretty quickly that I had NO idea what I was doing, so I tracked down a friend who I knew did a lot of 'erotic role play' online and, um, practiced. And she was a girl, so wow was it ever really, really weird. But if anyone knows how to describe sex, it's people who spend hours and hours doing it every night, and I figured as long as I was going to write this novel, I might as well do it right.
Long story short, she taught me a lot, then referred me to someone else who was a man and taught me more, and as a result, sex scenes are really easy for me to write.
And that, my friends, is how far I'm willing to go for my art.