A friend once asked me where I got the different personalities of the characters in The Gemini Bond, and which character I thought I was most like. I gave her a rather facetious answer. I said I was the cleverness of Rigo, the intellectuality of Trey, and the empathic abilities of Rissa. That's the easy answer.
I think that once I started to write, the characters just kind of developed under my pen (or cursor). Sometimes I had to tell Trey, "Back off, dude!" because he has such a strong personality. With Rissa, I had to constantly urge to step forward into her true self. With Rigo, I had to keep his deep rage in check on occasion. And with David, well, I just kept him tied up most of the time.
I think characters of borne of experience, but once the writer connects with the muse, or whatever etheric source these things come from, the characters become alive and independent of the writer's will. It's a really cool thing to experience as a writer.
Speaking of The Gemini Bond, the paperback version is coming soon. I need to do a second proof, and then it should be available after that. I'll keep you posted!