Many instructors struggle with crafting writing assignments that are accessible yet challenging for students. We suggest you consider the scale of the assignment — in terms of time, length, and scope — and the learning objectives of the assignment — what do you want your students to learn or show that they’ve learned through the assignment, and is it evident to them just what kind of project the assignment asks for?

Getting a Sense of Scale
Articulating Objectives
Taxonomy of Learning Objectives
Exercise in Assignment Design using Bloom’s Taxonomy (doc)