Taken from my blog:
I am writing a character-driven novel and in order to understand my characters I want to know everything about them. One thing I never thought of is: what do my characters dream about? Do they have nightmares? Wet dreams? Dream in color? Black and white?
Write a dream sequence. (The beauty of this exercise is that it doesn't need to make ANY sense as it is a dream.) Next, grab a dream dictionary. What have you learned about your character? Just let your subconscious write this for you. Maybe you'll be surprised at what you find out.
I did this exercise for my main character--the anti-hero. I put lots of thick fog in the dream and found out that he was walking through life disoriented. Funny enough, he is! Good job, subconscious.