I was more self-taught than anything. I've picked up a lot of information from reading stories and tutorials online, but for the most part I've learned by doing, and then talking things over with my sub. I'm probably fairly specialized in that regard, since I've adapted most of my internal whims to fit her interests and boundaries.
As far as life experiences, I think nothing helped nurture my dominant mentality quite like conducting an orchestra in college. The orchestra contained professors as well as students, and at first I was a little overwhelmed by its size and the combined experience of the musicians therein. But in the long run, I realized that if I acted with authority and confidence, they would respond to me by both putting on a good, artistic show, and also by showing up on time for rehearsals, paying attention when I gave instructions, and so on. It certainly is a different venue than bdsm, but the frame of mind is not as foreign as it may seem.