Decide on the settings for your story. Adventure stories typically have two to three settings throughout the course of the story. They will often begin in an environment that is familiar to kids, like the real world or a school, to be more specific. Other settings will slowly be integrated later on in the book, such as a magical world or a country far away from the starter setting.
Select characters for your book. Primary characters are usually regular children, allowing readers to relate directly to the story's protagonists. Secondary characters, who are introduced as the story progresses, are usually characters who fit in with your final settings. For example, if your second setting is a pirate ship, the secondary characters may be pirates and parrots.
Create profiles of your settings and characters. Draw images of them as you imagine them to appear, and record key traits that you would like them to have. Post all information up on a board in linear form, with the settings and characters that go hand-in-hand beside each other on the board.
Decide on your story's central plot. Write the events down as they come to mind. This can be in bullet-point form or in sentences. For example, your central plot may see the main characters getting transported to prehistoric times. Make notes about the challenges they will face upon their arrival.
Write down points that will come before and after the central plot, in bullet-point form or in sentences. This may include factors like what the main characters were doing prior to their adventure and what happens when they return from the adventure.
Write your story in full, following the plot notes that you made. Fill in the blanks with additional ideas, and clarify the story in complete sentences.
Put the story together as you see fit. This may mean typing it up and printing it out to read to children that you know. It may also mean creating illustrations to go along with the scenes and having it bound for a professional look.