You Will Need:
A familiar story, paper, and marker or pen
With your child, read the story half way through. Then, make up a different ending to the story together. Have your child dictate as you write it down (or have her write certain words/letters if she can) and ask your child to illustrate it.
Young children may have trouble getting started creating a new ending since they often like the predictability of familiar stories. Give them an example, and then brainstorm more ideas together.