My characters are not built. They aren’t picked out of a book of details and tailored to a situation. I’m sure they could be, and I’m sure many people have written books that way, but that’s not the only way to go about it. I’ve found it’s just as interesting (and more than possible) to allow a character to develop from a foundation of needs into a fully fledged person.
So it works like this.
First, you need rules. I’m not talking rules like “don’t name him Keith ’cause Keith is the worst name ever,” I’m talking “flies a ship.” Something simple, which only serves the purpose to allow the character into the story. The rules are sort of like your reasons for knowing the character in the context of the plot. Try and keep their number low as not to pidgeonhole yourself, but in the same way you don’t want to screw yourself over; use as many as you actually need to fit your purpose.
Next, you need to decide a few of the basics; things like gender, specific role, job, and physical attributes – the kind of thing you’ll use to describe your character at first glance. Some of these might be more fluid than others (I’ve changed the gender, job, rank, and even looks of many of my characters as I went on), but many of them will stick so give it a little thought. While you’re at it, remind yourself that unless it’s somehow related to a plot point it is okay to change things when you feel like it. These are your characters, and – much like you as a person and a writer – they will evolve and change as they experience things and are experienced.
At this point, if you haven’t already, you start putting them in the book. As time goes on and you put them into the story, you will come to points where you ask yourself (or your character) questions. The answers to these questions are what helps you develop your character further, as the character evolves as you write about them and think about them. It’s also important to remember as you write that even though some written scenes or notes may be of no use to the plot they may still be of use to you as the writer. Even things you don’t actually tell the reader have happened can be held to be true and worth remembering because they tell you something about the character a blank page and a snap choice can’t.
So you’ve got rules, you’ve chosen some basics and have changed or kept them as you’ve gone on, and you’ve written about your character (in many different ways); what’s next? Well, you keep writing and asking yourself and your characters questions. Just like you as a person learns about yourself through experiences and choices, so must you put your character through experiences and choices to learn about them – even if just as a thought to yourself.
Characters are just people you’ve invented, after all. 😉