Select a topic, theme or story, and map it out. No matter what the subject, be it fiction (Mr. Rabbit's Lost Hat) or non-fiction (How To Draw Dogs), brainstorm the story or idea, and outline the key details.
Use imaginative language. Children love to use their imaginations. Use sensory rich words that help the children picture what they are reading about. For example, "The tiny white rabbit poked his head out of his hole and looked up at the bright morning sun," evokes much more imagination than "The rabbit woke up and looked outside." Be careful to not get overly descriptive, as very rich language might confuse the children.
Write to the child's level. Keep the words and sentence structure as simple as possible. For example, rather than use the phrase "consumed the carrots," use "ate the carrots." Preschool children are learning the basic structure of sentences and reading. Don't confuse them with advanced words.
Avoid complex sentences. Analogies, similes and metaphors might be useful for an older audience, but they will likely confuse younger children. Keep the sentence structure simple.
Keep the story short. Children have a shorter attention span than adults. Limit the story to one typed page. This will also help keep the story filled with purposeful action-oriented content that keeps the children engaged.
Test the story out. Read the story to preschoolers, or have them read it and give feedback. Children will be honest and tell you what they liked/understood and did not like/understand. Enhance the story based on the feedback.