Determine what type of board book you want to write. List several ideas for the category. This should include illustration ideas or suggestions for unique concepts to convey the action and message of the story.
Outline a basic story in rough-draft form. This outline should include plot points. If you are telling a story, there should be a clear beginning, middle and end. If you are writing about routines, then identify the different pages you want to include in your book. For example, a book about a bedtime routine would take the reader through the different things a child would do to get ready for bed.
Write the book. Unless you are an accomplished illustrator as well as a writer, don't expect to be able to do the art for the book yourself. Most book publishers will hire their own illustrators. If the images are an important part of the story, give a short description of the type of illustration you picture on each page.
Proofread the story carefully. Check your word count. Make sure that each word is necessary to the story. Remember that the pictures will tell much of the story.