For writing guides on persuasive or argumentative styles of writing, see the OWL Writing Center web site from Purdue University:
Your research essay should be four to six pages in length. It must incorporate at least two outside sources, one of which must come from one of the HACC databases. Additional outside sources can be of any variety (book, magazine, newspaper, interview website), but they must be academic in nature (not Wikipedia!). Please try to adhere to the page limit and choose a subject that you can explain in that amount of space. Please choose a topic you care about and want to explore—your enthusiasm (or lack thereof!) will come through in your writing.