Share a story about yourself that is similar to a book you've read.
Change the ending: how would you change the ending of the story?
What happens next? Come up with a sequel for your story.
Place yourself into the shoes of one of the characters and write the story from their point of view.
Map out the story: draw the events of the story out in a map format. Have someone read the map and guess how the story goes.
Tell the story in a different setting. How would the story change?