Why include a dream in your novel? Dreams have no meaning. Right?
Wrong.
Dreams are a fantastic way of creating symbolism within your story. Something to make your reader think. With a well-written dream, you can reveal things about your character, and give hints about events to come.
You'll want to keep in mind that while dreams are illogical, you still want them to make a fair amount of sense to the reader. Now, because we are using symbolism, the dreams we create shouldn't be completely random. They must be somehow linkable to the plot, the character's history or future, or the character's relationships.
Nature is a great representation of life.
So, how might the character's life tumbling down be represented? A falling tree. Is it the character's fault that their life is tumbling down? Make it so they are cutting the tree down. Are the problems in the character's life now affecting the lives of others? Set the tree on fire, and when the character cuts it down the fire spreads through the grass and burns down other trees.
Now for an example from my own work.
The snake wove its way towards Ralta, its red eyes a pair of glowing ovals in the black night. It slithered up his leg, all the way up to his neck and coiled itself around him. Then another snake appeared, and another, and another until he was completely overwhelmed by the creatures. And there wasn’t any antidote. Why wasn’t there any antidote? Suddenly all the snakes were gone, and Saera was standing there with a bow in her hand, smiling and waving. And then a scream pierced Ralta's ear.
What does this dream tell us? Night is symbolic of evil, so we have learned that Ralta believes snakes to be sinister. The term "overwhelmed" implies that he feels trapped. He has been stuck in one place for too long. His wish for some antidote represents his desire to break free of his "prison". His sister Saera is smiling, which must mean she is happy. But if she is happy, then why does she scream? Perhaps this refers to an idea that maybe she seems happy on the outside, but Ralta believes she is not truly happy.
But then, what is the significance of the bow she is holding? Maybe Ralta feels safe around her.
I admit, I had never thought of all that symbolism when I actually wrote the dream. I simply wrote how the dream played out, and just now I interpreted it in a way that would give it meaning. So if you're writing a dream, don't stress too much about making it all symbolic. If it's written in a surrealistic style, the reader will naturally try to make sense of it.