What are your goals and outcomes for this assignment? What, specifically, can you articulate about what you want your students to learn, illustrate, or show you with this writing assignment?
Determine what specifics your students might need to know to do this assignment well. What are the conventions you want them to follow? Is there a particular format they should follow? Is there a page length? Does this paper need a thesis statement? Can you articulate for your students what the purpose of the assignment is? Do they know who the audience is?