In writing this essay, be sure to define key terms; clearly state your thesis; consider (in detail) the most compelling argument(s) for the opposing thesis; explain precisely why that opposing argument(s) fails; develop and explain a clear argument for your thesis; consider powerful objections to your argument(s); respond thoughtfully to those objections.
Essays should be clearly referenced (any widely accepted system of referencing is fine), and should draw at least in part on some of the arguments presented in some of the course readings.
It may be helpful to assume that you are writing for an intelligent, open-minded audience, and you are trying to argue why your view of the matter is correct or most rationally justified. Indeed, it might help to assume that your audience is slightly leaning to the opposing side, and so you will need to work hard to explain why the opposing arguments fail and why your side has the better reasons behind it.

Extra advice from the professor
Good philosophy papers must have a clear structure; they must have a clear argument; they must show a grasp of the literature, and they need to be self-critical.
Here is a “checklist” that may prove useful to you. The first things on the list may well correspond to the paragraphs in your actual paper. Consider it to be a sample outline.
Introduction that contains a brief description of the caseclear thesis statement. (I will argue that Deb’s abortion was morally wrong, or morally permissible)
Consider a major argument for the other side; explains it precisely and fairly
Raise a targeted, developed objection to that opposing argument, and explains why it fails (if you have 2 objections, then 2 paragraphs)
Gives a clear and precise argument for your view. really develop this argument.
consider a targeted and clear and developed objection to one’s favored argument
Thoughtful response is given to that objection
consider another objection to your argument (if applicable)
Respond to it.
Conclusion that accurately reflects what was proved in the paper.
Other stuff: in addition to the above points, the following will also be part of the matrix that Matthew uses to grade these papers.
did the student deploy a grasp of some of the relevant articles assigned?
did the student display general thoughtfulness about possible problems with others’ arguments and his/her own argument?
Clarity (individual sentences, and layout of the paper)
Did the student use paragraphs appropriately? For instance, I do not want to see you give an argument and an objection and a response in 1 paragraph. Instead, these are 3 things so I want to see 3 paragraphs.
Were any original arguments, objections, examples used?