Everyone else is doing it, so why not me?
Truthfully, I wing characters. My usual process is to come up with a plot and a setting and then think to myself, what sort of poor bastard would suffer most amusingly from being dropped into said situation? Of course, it becomes necessary to think this through for a longer story, because with more words come opportunities that demand some three-dimensionalization of a character. And, worst of all, Why? Why is this dude the comic relief, why’s that one always depressed–etc.
Before answering how I make characters three-dimensional–I proudly note that I’ve never been accused of one-dimensionality, though my physical descriptors are often lacking–there’s something else that needs considering first.
Fiction is a way to distill reality. Take one aspect–a theme, an attitude, an event–and amplify it a thousandfold till the reader has no choice but to accept your rules for the length of your words. The best books color the way their readers see reality itself.
In this context, fictional characters are distillations of specific personality types and attributes. Think of a caricature: it’s unarguably a person, and more importantly a recognizable person, even though we’d never see something like it in reality.
So yes, you should draw off the people you know to help create your characters. But you should never model characters so directly that they essentially are the person (albeit given your motivations). We see real people every day. We don’t want to see what real people do in situations; we want to see distortions. Amplifications.
In some cases, this may be a mere physical attribute: too beautiful for reality, perfect red hair; more often, it’s a characteristic emphasized to a point where this single thing can be considered the defining attribute: an alcoholic so unapologetic that even the liquor stores won’t let him in, a mother whose obsessiveness gives her kids the worst Oedipal complexes….
Note that in these examples the chosen trait drives a conflict.
This is key. Prose may be allowed to get away with a higher word count, but that doesn’t mean you can sneak useless sides into the equation. Shakespeare’s gravedigger (‘Hamlet’) had a role to play, too.