The simplest and most honest answer to that question would be, “I don’t really know. They just come.” But let me try to do better than that.
Years ago, I learned an important lesson by reading Dick Francis’ mystery novels: Every character in your book, no matter how minor, you must view and write of as a real person. Even if the character is in the story so briefly that you don’t even have to give his name.
A common feature in a lot of books that stink is failure to observe this rule, because the author is interested only in himself. You wind up with some improbable hero or superwoman showing off at the expense of all the other characters, who are only there as stage props. Books like this should never be published, but some always make it through the net, and too bad for you if you’ve bought one.
I don’t sit down and write up a thorough biography of every character in the book. If the plot demands that someone come along to be the new captain of Lord Chutt’s Wallekki bodyguard, then I introduce a character to do just that. I give him a name. And then some funny things begin to happen.
Often, once he or she has appeared in a few scenes, I take an interest in this character. So it was with a man named Bassas in The Throne, Lord Chutt’s new captain. To my surprise, it turned out that Bassas doesn’t like Lord Chutt and has but little respect for him. As the circumstances around him changed, and he came to see more things that he hadn’t seen before, Bassas grew discontented with his lot: in fact, he didn’t much care for working for the bad guys. He hasn’t been able to shed the old tribal sense of honor that was drilled into him as a boy.
See what I mean? Bassas went on to do some things I never thought of when I first introduced him. He’s very different from his predecessor, who was a thorough-going rogue. I wonder what he’ll do next.
This all sounds very easy to do. All it takes is thousands of hours of reading quality fiction and thousands of hours of trying to write it. How do you get to Carnegie Hall? Practice, man, practice!
But it all starts with a determination to see your characters as real people. Just because they’re fictional doesn’t mean they can’t be real. They have to be, or your story won’t work.