Reading through these comments, I have to tell you that they all seem very one-sided. All this talk of your first time being your worst time. I mean, sure, maybe some times aren't that wonderful... but can they ALL be that way? Who hasn't seen the dramatic de-flowering of Justin by Brian on Queer As Folk?
We should all be so lucky, right? Side note: if the guy you choose pours Poland Spring all over himself with little-to-no care for his hardwood floor... well, you're in for quite the night!
In the end, I think there are two kinds of "first times" we can hope for:
1. The dual first time
This was luckily my experience. You and the guy you lose it to are both newbies. Neither of you has topped or bottomed. Or at least the top hasn't topped and the bottom hasn't bottomed. In this scenario you both will bumble and fumble around, but at least be able to laugh about it as you get the steps right. Think Bel Ami (without all of the Dutch scenery, and foreskin). Have fun! Sex is a crazy crazy thing!
2. Mrs. Robinson Plows You Good
On the other hand, it can also be good to have your first time with someone who can barely remember their first time - as is the case with Brian and Justin above. This person can teach you tricks. How to breathe, relax, focus. Or, on the other hand, they can do what they will with you and make you feel like a Kleenex with limbs. But, staying upbeat, I imagine a guide, a mentor, someone who takes you through the steps and is caring and careful about it.
What's funny is that my first time was a mix of the both. My boyfriend at the time told me "I want you inside of me." And the way he said it was so experienced that I was like - my God... here we go. Afterwards I found out that it was actually his first time too - both a relief and almost a dammit moment. I had been so nervous while going about everything, assuming he was laughing on the inside.
Of the few guys that I was their first time, I was always careful. Always performing status checks. Because I know it's a big deal... ESPECIALLY for a bottom. For a top, you're trying to fit the peg in the circle. The worst you have to worry about is your aim and rhythm. No pain involved. But for a bottom - there's a whole host of sensations you are experiencing.
Either way, I wish you all the luck in the world - be it a version 1.0 or 2.0 experience. And then, as you said, once it's said and done, you can turn into a total whore and really find your mojo.