Students often aren't aware that their professors don't consider Wikipedia or professionally biased websites to be a reliable resources, so always discuss your requirements in advance and make sure every student has a written copy or a digital file to refer to. Sources should be current (no more than five or ten years old depending on your field) and relevant to the student's topic. Students should integrate at least one quote or reference per paragraph, providing necessary author citations and drawing logical links to the paper's thesis statement. Students should acknowledge at least one alternate viewpoint and deal with it in the context of the paper. Any new information should have a source -- no appeals to "common knowledge" or generalizations about people or groups of people without statistical data.
Papers should adhere to MLA or APA format. The introduction should summarize the paper and must include a coherent thesis statement that the rest of the paper supports. Body paragraphs should provide adequate background information unless the assignment guidelines instruct otherwise. Sentences should not be redundant, contradictory or non-sequential. Paragraphs should end in students' own words rather than quotes and should transition fluidly to the next paragraph. The last paragraph should sum up the argument and paraphrase the thesis conclusively.
Students should vary sentence structure, focus on complex and compound-complex verb constructions and avoid simple sentences whenever possible. Writing should be efficient, specific and precise. Unless the assignment calls for the passive voice for scientific objectivity, students should write their sentences in the active voice and use transitive verbs as often as possible, avoiding linking verbs and "to be" verbs. The tone and voice should be consistent and the paper should be geared toward a specific audience.
Students should display an appropriate command of vocabulary suitable to their level and field of study. Words should be diverse; students should avoid using the same key word, or form of the word, in consecutive sentences. Teach your students about the advantages and pitfalls of elegant variation before assigning a writing project so that students can avoid redundancy and awkward evasion of key words. Words should be used according to their meanings. Students should avoid colloquial phrases and cliches.