One of the things I like about teaching is the opportunity to read lots of writing books and distill what each one is saying, and choose what is useful to use in class. Sometimes I'll have one book that I use as a base text, or that we need to use as a base text - like a starting point. In first year fiction writing, we use Garry Disher's book Writing Fiction. It's a great starting point. This year I'm teaching Myths & Symbols and although I have four or five huge texts on world mythology, I choose one as my base text for "lectures" (because I don't lecture like professors do, I talk a lot about stuff that interests and excites me). It's a good text - out of all the ones I own, it covers the subject with the best information in the clearest form.
One of the traps you can fall into, as a teacher, is sticking to one text too closely, as if it's a bible of some kind. Of course there are authors out there, like John Truby and Robert McKee, who teach absolutely from their text - usually the writing course comes before the text anyway. There are so many ways to teach writing! There are books that focus on character, on setting, on dialogue, on plot and conflict. There are books about picture book writing, and about writing for young adults. How does the beginner writer ever know which one is "correct"?
Well, they all are. And they all aren't. Some books will speak to you, will tell you exactly what you need to know at the moment you need to know it. I read Elizabeth Lyon's book, Manuscript Makeover: Revision Techniques No Fiction Writer Can Afford to Ignore, a couple of years ago, just when I needed a new perspective on self-editing. I read Eric Maisel's book, A Writer's Paris, because I was going to Paris and wanted a writer's perspective on where to go for the best inspiration (Eric obviously had never had hot chocolate at the Place de Bastille though). That's the benefit of building a library of these books.
However, they're not cheap. A friend and I share our library and try to make sure we don't duplicate purchases. That way we can borrow and lend, and know we've got a huge range of knowledge available at a lesser cost. I advise students to read some of the books first before buying. You'll soon know if the book "speaks" to you, if it's going to provide what you need. Some you will come back to, time and again, some you will read maybe once and then move on. A book can be a great teacher - and not just a writing book. A great novel can also be an excellent teacher, if you take the time to read it like a writer.
Getting back to the "He said..." of the title, I have seen examples of teachers who I think are problematic. These are the teachers who are only interested in teaching what they know and do themselves. That's it. Nobody else's theories and practices are relevant to them. It's a case of DO AS I DO. I think that's dangerous. All you turn out is clones. Publishers don't want clones. They want writers with fresh new voices who will take risks. How do you take risks? You learn the rules first, you read widely and critically (of novels and how-to writing books), you take what is useful for you, you bend it into what you need, you think laterally, you experiment and explore, and you write the story that's in your heart.
And then, hopefully, when you're published, you can thank your teacher. Because there's nothing a teacher loves more than celebrating their students' successes. Trust me, a jealous teacher won't teach you much at all. They can't afford to...