Three basic rules:
1. There are no superficial people; there are only less articulate people– in fiction.
2. Even dumb characters have to say interesting things.
3. Dialogue has to accomplish more than one thing in order to earn its keep (see on writing dialog, an earlier entry).
One character asks a question in direct dialog; where do these possible answers lead the story and the characterization?
“Do you live around here?”
–Hey. I wouldn’t be caught alive in a place like this, pal.
–I’ll have you know, young man, that my grandfather built this house. I have never lived anywhere else. Never cared to.
–What kind of question is that? Did you think I was sleeping on the street? I look like a bum to you?
–Sure do. That little yellow job over there is mine, all nine hundred fifty square feet. Shingled the roof myself, which is how I come to do such mischief to my back.
–The hell out of my face.
Two kinds of exercises that are useful: take a well known character in literature and try to get them to answer similar questions. How might Captain Ahab reply if a stranger were to ask him if he’d like some coffee? How would your main character? The other thing to do is construct twenty possible answers that take the storyline in twenty possible directions. Something to get you started below.
“What did you get up to over the weekend?”
–“There’s mustard on your tie, did you know that? Mustard.” (father and teenage daughter)
–“Amazing. You look like a functioning human being, and yet you comprehend nothing.” (man and woman being pursued)
–“You know very well where I was this weekend, and let me tell you that your grandmother was very dissappointed not to see you at her tea party. She made that jello you like so much, with the grated carrots and the marshmallows, and then she had to eat the whole thing herself.” (mother and adult son)
These exchanges might work in a given piece of fiction if they moved the scene along and contributed to characterization. See what you can do; make up a character and see how they answer the question.