I promise I don't keep a dream journal, but I do think about my dreams and how they can help me write when I'm awake.
I heard once, that everything in your dreams is something or someone that you have seen in real life. Your subconscious takes bits and pieces of real life and smashes them up into a dream sequence that makes sense, in a dreamy kind of way.
Usually, I can't tell you exactly where each of the pieces of my dreams come from, but in one recent I was pretty sure I could pinpoint the parts in waking reality.
In this dream, I was standing on the front porch of a house, probably mine, or maybe soon to be mine. My son was nearby pounding a garden ornament with a pickax. I had to yell his name three times before he would stop.
Now, the pickax came from Minecraft - this was evident by the pixally look of the ax and also the fact it was flat. The porch looked jus like a porch that I stood on years ago when I was a girl, and the lawn ornament was a figure I'd been drooling over at one of those outdoorsy stores. And the yelling three times - that came from a very real incident when I needed to get my son to come. He wouldn't stop bickering with his brother until the third time. It was frustrating.
"Write What You Know"
Like this vivid dream scene, we can take bits and pieces of our life and put them together in a new interesting way. The pieces don't even have to be "real" (the Minecraft Pickax), they don't have to "true" (the porch wasn't mine in reality, and my son has never stood on it), but the resulting scene should be charged with emotion (the experience of taking three times to get a kid to stop). This is what we are creating when we write fiction.
Because it's believable.
I write about, with, for, and around kids all day. (Well, maybe I do the dishes too. Sometimes.)