The short answer? They don’t.
The longer answer? They don’t. Well, not really.
The complete answer is a bit complicated, but here goes. Back in the day, lo these many years ago, before I was published, before I’d submitted a single query letter to an agent, before I’d started writing any book at all, I realized that I had no clue how to write.
I desperately wanted to be a writer, and made a solemn vow to become a published author, but I had absolutely no idea how to, you know, actually do it.
So I did what a lot of people do: I started reading. Not the mystery that I longed to write—though I did that, too—but books about writing. Julia Cameron’s The Artist’s Way, Robert Ray’s The Weekend Novelist, Anne Lamott’s Bird by Bird, and numerous others that I could name if I got out of this comfortable chair and walked all the way over to the bookcase. I read all that advice—inhaled it—and when I sat down to put pencil to paper, I still had no clue what I was doing.
Thus started my pre-published era of writing. This was when I wrote the 6.3 books that are now languishing in the deep dark corners of my computer. This was when I joined the Guppies, an online chapter of Sisters in Crime. This was when I joined a local writers group. This was when I started hearing people say things like, “That guy who fired me, yeah, I put him in my first book as the murder victim. It was cathartic,” and “In one of my books I made the mean girl in high school into a waitress in a run-down diner. It felt great.”
I thought about all that, but when I finally got brave enough to start writing my own stuff, I never got around to thinking about inserting people I know into my books. My characters tend to develop first as a skeletal role—best friend, neighbor, aunt, coworker, whatever—and then I figure out what personality would best fit the story. Shoving someone I know into one of those roles isn’t likely to fit. If I dropped a friend into a book, she would walk and talk like my friend, and that could drive the entire thing in a direction I didn’t intend.
That said, there have been times when I’ve used bits of people, but not so much personalities as physical attributes. It works like this. I’ll be writing a scene and a new characters walks in. “Huh,” I’ll think, pausing in my typing and staring off into space. “What does he look like? Hmm…” (I need to have some idea, even if it doesn’t get on the page.) “Let’s see…how about that summer intern I worked with 15 years ago? Don’t remember his name, but I remember what he looked like. Sort of. That’ll work.” And I’m on my way.
So that teeshirt you might have seen; “Be nice to me or I’ll put you in my novel”? With me, you don’t have to worry about that happening.
Not really, anyway.