I’m often asked, by people who don’t themselves write, something along the lines of “Do you model your characters after people you know? Family, friends, rivals?” Usually the question is asked with a knowing grin and mischievous gleam in the eye. And so more often than not, those asking the question are disappointed when I say, “No, I almost never do that.” That’s the truth, and here’s why:
It might be lots of fun, at least in theory, to make an autobiographical protagonist fall in love with a woman modeled after my wife, or after that girl in high school who never noticed me despite my repeated attempts to draw her eye; or to make my main villain a dead ringer for the college professor who gave me a B- in composition when I KNOW I deserved an A; or to pay homage to my mother or father with a kindly older character. I have found, however, that the characters I try to shape in the images of people I know are the characters who are least likely to develop on the page into fully realized human beings. In other words, writing people I know tends to result in lousy characters.
On the other hand, those characters who I create wholly from my imagination, who I create on their own terms, without any hidden real world agenda, are the ones who come to life, who start doing things that surprise me and drive my narrative in unexpected directions. They are uniformly my best characters and the ones I most enjoy writing.
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http://www.dbjackson-author.com/blog/index.php/2012/02/07/writing-tips-character-development-starting-points/)
I really love this point in this article in particular. I don't think people who have never written fully understand this concept. As writers we tend to talk about our characters like when we write we have full conversations with them, arguments over this and that, say things like "I wanted to do this, but my character insisted that he have his way". We don't mean to say that we're schizophrenic and our characters are bossy voices in our head that literally turn our stories ways in which we don't want them to go. (Even if we sarcastically say it as such sometimes, because hey, rewriting and switching directions is a lot of work. And our characters become so real to us.) What we do mean is that once you start creating, once you're fully inspired - your brain kind of just tends to run wild with it. Like a leaky faucet, you try to turn it off but it's still always there, dripping out one drop at a time, in the back of your mind.
For instance, the story I'm writing currently I wrote a five-paragraph synopsis on the first day of my inspiration. Then, when I started developing the actual personality side of those characters, I had to go back and edit that synopsis. No, character A would never make decision B. Decision B would then not result in consequence C. So you edit and fix and rewrite. And so in that way all good fiction is character-driven, no matter how awesome your plot is.
It can also be viewed like this. I had major characters plotted out and my revised synopsis and then last week while driving, I saw graffiti on a wall. Nothing awesome, nothing important, nothing I haven't seen a million times in my life. But there was the leaky faucet in the back of my mind and suddenly: this new character starts forming in my mind, a brand new way to advance the plot in certain situations, a moral counter for my protagonist and a great way to create suspense. Suddenly, the entire second half of my story went a drastically different way.
So when we say as writers that we have no control over our writing, it's really just a way of saying that our inspiration is totally unpredictable, and that's the way it should be. If your story looks the same when you finish it as when the first seeds of the idea started growing in your mind, you're doing it so totally wrong. Stifling your creativity and not trying out new ideas and concepts because "your outline doesn't include it" is the easiest way (but not the only way!) to make a shitty, predictable set of prose that no one wants to read.