I chose Alex for a few different reasons. One is that I wanted something that could be unisex so that when I start to transition, ppl who see me as male won't wonder why my name's Christina, and likewise, those who see me as female won't wonder why I have a male name. Another reason is that one of my fave video game characters (Axel from Kingdom Hearts II) has a name with the same letters, just rearranged. I didn't want to take "Sora" or "Riku" (my other fave characters from the same game) because they're Japanese names and I didn't want ppl to be confused like, "How did you, being Caucasian, end up with a Japanese name?" My 4th fave character's name is Roxas, but I figured anyone who knows the game would know exactly where I got it from.

I wanted something common enough, but not with zillions of ppl sharing the same name. I also like the way Alex sounds both soft and strong. My brothers names are Michael and David, so I knew I wouldn't go with either name, even if I had wanted something so incredibly common.
All in all, I guess Alex just spoke to me. I did try the baby name book thing, but the one I was looking at is from the 80s, so it wasn't totally helpful. Now, my middle name is a whole different story. I originally selected Rene because it sounded good with Alex and my last name. But after I used in in my username on this forum, I decided against it. It sounded a little boring and weak. So I went for Jamison instead, remembering that FTM author named Jamison Green. I liked how sharp it sounded, and I took into consideration my affinity for J names. Besides, it worked better with my initials: AJB sounds more like initials than ARB. ARB sounds too close to the name of that restaurant, Arby's. LOL.
Anyway, that's how I eventually chose Alex Jamison. Now, if only I could change my username.... xD