Students WANT to give us what we want. They are just not always sure what that is.
Here is an excellent suggestion from Mike (a history teacher) that I am going to incorporate regularly into my classes:
I have found that after the first test of the semester, I select the best student essay answer and present it to the class, not identifying the student. Preferably, if there were several essay questions, I select the best of each and present it on the screen–this tells the students what I consider a well-formed essay and also what content I thought was appropriate and addressed the question best. And it came from a fellow student, not the professor.
Another windfall from this is the student whose essay is displayed is very proud and encouraged and wishes to keep up the same standard in the future.