Give explicit directions so students can tell whether they did or did not meet your standard. Vague directions and hints are both unfair and counterproductive.
If material is essential for students to know, present it at least once from each primary learning mode. It’s not fair to expect all students to learn well the way you do.
Don’t grade student writing on factors you don’t teach. For example, don’t evaluate work for creativity unless you teach all students to be creative.
Evaluate for a grade only writing in your chosen instructional genre.