I’m a little bit afraid to write about my teacher, David Foster Wallace, because he was important to me, and I don’t want to mess it up. I was afraid to take his class at Pomona College too, for basically the same reason. To get in, you had to audition: students submitted short stories to nab one of 15 spots. I figured if I was rejected, I’d never be a writer. So I cooked up a plan: show up for his office hours, ingratiate myself, and edge out other kids trying to get in the class.

The plan didn’t go brilliantly. I was too nervous to make a good impression. I’d bought Brief Interviews With Hideous Men with a gift certificate I’d gotten for high school graduation because I thought the title was funny (much later I’d tell Wallace this and, in one of his occasional lapses of midwestern modesty, he grinned and said: “That was a really great title.”).

He’d pass around a handout titled Your Liberal Arts $s at Work, which collected students' solecisms from the week

Brief Interviews was my first real encounter with experimental fiction. It freaked me out. At 18, I was a cocky lit kid who hadn’t had my head kicked in by a story since I was a child. But when I figured out these stories wanted me to do real work – hard work and lots of it – but that I would be rewarded for it, I’d started thinking about fiction in new ways. Or really in old ways – when I was a child, my favourite stories were the ones that were strange and exciting and tough to figure out, which felt right, because the world was often like that, too. Children are ideal readers of experimental fiction because childhood itself is experimental, whereas teenage smart alecks are terrible readers of experimental fiction, because they’ve deluded themselves into thinking they’ve figured everything out (adults are even worse). But Wallace’s stories made me feel like I was reading as a kid again. I kept buying his books.

And now there I was in his office. I asked him whether there was anything I should know about submitting the writing sample. He said he thought the instructions in the course catalogue were clear. (They were. Everything he wrote was – Wallace spoke, emailed, and composed course descriptions in the same precise style as his famous prose.) I wasn’t ready to leave after 90 seconds, so I asked him how he’d be evaluating the submissions. He softened. I think he’d figured out my whole pathetic enterprise. He told me that judging the merits of these short pieces was about as exact as throwing them down the stairs and seeing which ones made it the farthest, then tacked on a warning: “Make sure you check it over for typos and errors.” And he then tacked on another: “More than once.”

Wallace was famously obsessed with English usage, and it showed in his teaching. Each week he’d pass around a handout titled Your Liberal Arts $s at Work, which collected solecisms perpetrated by students in the previous week’s writing. We’d quickly scan the sheets for proper nouns — when you recognised one of your characters’ names on the page, you knew you were in for a public scolding. “You do not make grammatical errors when you’re swinging for the fences,” Wallace said during the first class, only instead of “errors”, he used a word I’m assuming is unprintable in British newspapers. I wrote this admonishment down in a notebook where I collected things Wallace said that I never wanted to forget. I think most of the other kids kept one of these going too.

Wallace had his reasons for grammatical zealotry in the classroom, but it wasn’t about being Gradgrindian or prescriptive. I think Wallace is rightly understood as a moral writer – so much of his work explores what it means not just to be human, but to be a good human – but he was also an ethical one. He was always talking about a writer’s responsibilities: the responsibility to be clear, the responsibility to be interesting. Because Wallace’s work could be difficult, because he asked the reader to work, he wanted to be sure he was doing his work too, saying exactly what he intended, in a way that was compelling. Another entry from my notebook: “If you’re more interested in what you’re saying than the person listening to you is, you’re the definition of a boring person.” I remember feeling like I’d been slapped with a stick.

The first thing Wallace asked me that first day, when I showed up in his office angling for a place in his workshop, was why I wanted to take his class. When I told him I wanted to write children’s books, he winced and said he didn’t know anything about writing for kids. I told him that I didn’t want to learn how to write for kids, I just wanted to learn how to write. He did teach me how to write, or at least how to go about writing, and it’s a lot tougher than putting together a clean and well-wrought sentence. It’s as tough as having a real conversation. Because to have a real conversation, you have to figure out what you actually care about, and then you have to figure out how to make somebody else care too. And we all know how scary that is, right?

• Mac Barnett is a children’s books author. He graduated from Pomona in 2004. His book The Terrible Two, with Jory John and illustrated by Kevin Cornell, is published by Amulet Books.