One of the most fascinating catechetical texts from the patristic era (or any era) is St. Augustine's On Instructing Beginners in the Faith (an older translation can be found online here for free, but get Canning's translation if you can). It was written around 400 AD in response to a weary priest in Carthage named Deogratias, who had written to Augustine because his catechetical instruction was, he feared, becoming tedious and boring.
Augustine's response provides us with a wellspring of wisdom for anyone engaged in the work of catechesis today. Here I want to introduce the book, though I'm sure I'll return to it again at many points in these pages.
The weary catechist Deogratias is writing to ask Augustine specifically about the kind of instruction he should give to those who want to become catechumens. In the fourth century, the catechumenate consisted of four stages: a person went from being a pagan to a catechumen, then from a catechumen to a baptismal candidate (a "competens" or petitioner), and then from a candidate to a baptized "neophyte." One could be a catechumen for several years, sometimes even most of their lifetime. The pre-baptismal candidacy period typically lasted the eight weeks of Lent, with most baptisms occurring at Easter.
Deogratias is here asking specifically about the kind of instruction given to those who are going from the first to the second stage: from pagan to catechumen. We don't have much from the patristic period in the way of this kind of literature: it's not evangelism per se, because people are already approaching the church asking to be begin the initiation process. But it's also not the more rigorous stages of the pre-baptismal catechumenate—where in some places (Jerusalem, for example) they would attend lectures for three hours a day throughout Lent!
The Latin title De Catechizandis Rudibus refers, then, to teaching in this earlier stage, as opposed to the kind of pre-baptismal catechetical instruction that we more typically with catechesis. (This does not mean, I suggest, that this stage of catechesis is any less important than the pre-baptismal catechumenate). Rudibus here just refers to the "beginners," those just getting the "rudiments" of the faith. It doesn't pertain to any particular class of people. Augustine mentions potential candidates who either have a really good educations or are from the run-of-the-mill schools. Some even have quite a bit of knowledge about Christianity, which they acquired from reading the Scriptures or Christian authors.
When such pagans did decide to become catechumens, the bishop or priest would inquire into their lives, to see how they lived, what their profession was, etc., and to discern their motives for becoming Christian. But they would also give them a basic overview of the Christian story.
Deogratias is asking how to present the Christian story to these inquirers. Where should he begin the story and and where should he stop? After giving the historical overview, what sort of motivations ("exhortations") should he give for becoming Christian? What sort of requirements ("precepta") should he prescribe for how they were to live now that they've joined the church?
Augustine, like a savvy physician, reads these symptoms, and has good practical suggestions for how to make his teaching less boring. But he also insightfully diagnoses the theological problems at the heart of Deogratias' lackluster teaching. Above all, he turns his response into a theological meditation on the instructor's participation in the humility of Christ, and how to turn one's heart toward the love of God and neighbor as one engages in the task of teaching these "rudes."
The book is roughly divided into two parts: In the first part, Augustine gives advice on how to give the narrative explanation of Scripture (from Genesis to the contemporary church); then what kind of exhortations and precepts to give (focusing on the love of God and neighbor); and then how to have a "cheerful disposition," for which he gives six possible causes and solutions.
In the second part of the book, he gives two "sample speeches" of these kinds of narrative summaries of the Scripture—one longer and shorter.
Again, I plan on returning to the content of this work in more detail, but I wanted to preface any of those remarks with a bit of historical background on the context in which he's writing. Even given his different historical circumstances, however, there is just too too much practical and theological wisdom here, which will be a boon to any catechist. I simply can't recommend this book highly enough.