Think about the purpose of the assignment. Good papers accomplish their purposes. Think about your audience. Your instructor is almost always your audience, but sometimes the instructor designates other audiences for you to consider. In either case, remember that readers want to be interested and respected.
Good papers get through to their intended readers.
Use a moderate tone unless you have strong reason otherwise. In general, write as a reasonable person writing to other reasonable people about something interesting. Good papers usually persuade readers that the writer is levelheaded. Be as specific as your purpose allows. It is difficult to strike the right balance between general statements and detailed ones.