I compared this idea to Dorothy and the Wizard of Oz - how the wizard was doing all sorts of things behind that curtain that Dorothy didn't see (well, at least, not at first). The point is, we, the writers, are the ones behind the curtain, doing all sorts of research and fleshing out of characters that the reader might never be fully aware of.
Today's class buzzed with energy -- it was so fun to see the students excited about this. I passed out my list of character questions and asked them to add 10 of their own. Then, we shared. I couldn't write them down fast enough. Hands going up all over the room, eager to share. They added some great ones, like these:
* What's the posture/gait of the character?
* Does the character experience road rage?
* How many languages does the character know?
* What kind of shoes does the character wear?
* Does the character text?
* What's the biggest secret the character has been holding onto?
* Does the character have a healthy self-esteem?
And on and on. I wrote down at least 50 new questions, for myself, that the students came up with.
Bottom line in all this -- know your characters inside and out. Know what their reactions would be in a given situation, what their hopes are, their fears. Once you know the characters that well, they'll start to write themselves. They'll start making decisions on their own, start living and breathing and acting more like real people. Which, even in fiction, should be a top priority. That the characters ring true.