There's all sorts of "tricks" I've used to keep it from becoming Twister: The Adult Edition. (Although now I can't help thinking of Bill & Ted II and Keanu playing Twister with the Grim Reaper, only naked...)
Oh, pardon me, did I trail off there? Anyway, I'm with Filigree in that for my characters, emotional connection comes first, even when it's not love or anything like it. They click in some way, or have that fairly rare animal-like lust for one another and choose to act on it.
I'm also seriously into my point of view character's thoughts, memories, hopes, fears, and physical sensation. I can spend a page, easy, on what a fingertip brushing a nipple does, and two on a character's first up-close look at a scar hidden by clothing.
I'm also mindful of the physical. Even when my characters are fine physical specimens (not in my current WIP), they're not gymnasts. They use only a few positions, settling on ones which most please them early on, with some variations on angles--sort of like real sex. (OMG!) I minimize descriptions of the Tab A-Slot B variety, focusing a lot more on how the POV character experiences the lovemaking.
Maryn, inside heads