I'd start moments before one person (or both) confessed how they felt about the other, and going through that whole mutual ecstasy together. I really enjoy that part of the ride. Then again, I even love the anticipation and unknowing that lead up to that revelation (assuming that it is indeed requited love, since I've been down the unrequited one too many times)... so I guess I wouldn't change anything.
For me, though, the intimacy comes long before the sex... I mean, there's the hanging out with friends (for me, usually), getting to know each other's sense of humor, realizing your attraction, then starting to share things with that person. Building an intimate friendship before anything romantic happens... that sets me on fire.
