Depending on what university, department or school you study at, chances are there’s a set list of marking descriptors that are used to determine your essay grade. They are usually publicly available (google your institution and ‘essay marking descriptors’), and detail what your essay needs to do in order to achieve a C or B or A. The descriptors of the school I currently work at, for example, Edinburgh University’s School of Social and Political Science (SPS), can be found via this link. What you are probably not aware of, however, is that hidden within them is some really sound essay marking advice.