How do I write a sex scene?

This is a question I found myself asking, as I write a fairly detailed sex scene in my novel.<br>I have written several before, but it's not necessarily something you can plan out. Many of you have probably thought about how you would have sex with a fictional character. But how do you write a sex scene?<br><br>I don't know if anyone can really answer that, but I'd be curious to hear your thoughts.