Miss Mango, you are an inexhaustible source of thread-starting questions!
The first time I consented to sex (not when I lost my virginity), it basically just happened. Ktspktsp and I had just "gotten together" a few days prior, while my mom was visiting and staying with me. We were kind of waiting for her to go home before trying anything, but one day I just went over to his house and we got naked and... yeah.
I think we both knew that it had the potential to happen (it was at like 11am--I guess we were horny!), as we had both showered, shaved, and cleaned up real nice right before that, but it wasn't "planned" by any means.
I ended up skipping a lecture that I was a TA for, which was kind of bad, but I never did that again since. I figured it was for a good cause.
That was almost exactly 4 years ago, on his birthday, April 13th!