On René Descartes's Rules for Direction of the Mind (1628): Mark Linsenmayer hosts Episode 223 at The Pariially Examined Life, A Philosophy Podcast and Philosophy Blog.
"This early, incomplete work lays out 21 rules for careful thinking (out of a planned 36) with extensive commentary on how to apply them. It is extremely helpful in figuring out where Descartes is coming from in the Meditations, and it lays out the foundations for both analytic philosophy and the emphasis on quantitative analysis in modern science."
(via Penny Parker at Great Conversation Reading Group)
See Descartes, Rules for the Direction of the Mind, Method of Rightly Conducting the Reason, Meditations on First Philosophy, Objections Against the Meditations, and Replies, and The Geometry, in Great Books of the Western World (first edition, 52 Vol., 1952) volume 31, (second edition, 60 Vol., 1990) volume 28.