Venerable Fulton Sheen's "How to Think" (1955) from Life Is Worth Living:
And "How to Improve Your Mind" (1956):
All things considered, they are both pretty good. The first is better than a lot of 'critical thinking' resources you find floating around. The second is a discussion of the virtue of studiousness (studiositas), and has the classic line, "That's when knowledge begins to spoil: when you've lost touch with the common man."
The 'Venerable', of course, was given him in June 2012; it is given after an investigation into whether the person in question lived a life that is in some way exemplary of the major virtues. And last week a major step toward beatification was completed as a purported miracle passed preliminary investigation, which was an examination by a board of medical experts to determine that it is not a trivial or common occurrence, and was forwarded for the next stage of investigation, in which a board of theologians will examine it for theological significance. Of course, there is no timetable for these things. Caesar Baronius, the ecclesiastical historian, has been stuck at the Venerable stage for something like 270 years now, and Maria de Agreda for something like 340.