12 Writing Prompts to use in December. These can be used individually with the class, in literacy centers, or as a snowball writing activity. For snowball, have students write add one or two sentences to the story prompt they are given, crumple the paper into a snowball, and throw to the front of the room. Then all students will choose a ball, open and read what has been written so far, and continue the story by adding one or two more sentences. This process is repeated as many times as necessary to finish the story.