I was reading Jacqueline Broad’s excellent book on Mary Astell, when I came across Astell’s six rules for thinking, and decided that they were in fact perfect advice for students writing philosophy essays. So here they are (from Jacqui’s book, pp.31-32 – references from footnotes are in square brackets).
- To ‘Acquaint our selves throughly with the State of the Question, have a Distinct Notion of our Subject whatever it be, and of the Terms we make use of, knowing precisely what it is we drive at.’ [Proposal II, 176]
- To ‘Cut off all needless Ideas and whatever has not a necessary Connexion to the matter under Consideration’ [Ibid] This entails that we ‘Reason only on those things of which we have Clear Ideas’. 
- ‘To conduct our Thoughts by Order, beginning with the most Simple and Easie Objects, and ascending as by Degrees to the Knowledge of the more Compos’d.'[Ibid]
- ‘Not to leave any part of our Subject unexamined.’ [Ibid] This entails ‘Dividing the Subject of our Meditations into as many Parts, as we can, and as shall be requisite to Understand it perfectly’ .
- Always to ‘keep our Subject Directly in our Eye, and Closely pursue it thro’all, our Progress.’ [Ibid]
- ‘To judge no further than we Perceive, and not to take any thing for Truth which we do not evidently know to be so.’ [Ibid]