Say what? Or, just as important, say how?
How your characters talk is just as important as what they actually say. In fact, good dialogue can be defined as the right speech content expressed in the right words. And good dialogue can do as much to create strong characterization as can description and exposition put together. Speech is a powerful expression of personality.
Consider, for example, this situation: Your character Harry has a car accident. Later that day, as the bashed-in car sits in Harry’s driveway, the doorbell rings. Harry opens the door to his Uncle Jim. Jim’s first words are one of the following:
“Harry, what happened to your car?”
“Jeeze, that car looks bad! Gonna set you back ...