Wallace taught creative writing for most of his career, first at Illinois State and later at Pomona College, and his advice to students was less about inspiration than attention. He wanted them to notice how good prose is actually built.

The Direct Answer
Read closely, revise hard, and keep a usage dictionary handy.
Drawn from his teaching years and his interviews on language and craft.

Pay Attention to the Sentence

Wallace's first piece of advice was to read like a writer. That meant more than reading widely, though he did plenty of that. It meant watching how a sentence gets built and how its clauses join. He thought most readers skate right past that machinery, and that learning to see it was half the job.

His syllabi backed this up. They're demanding documents, heavy on grammar and usage, and students kept them, which is why several are online today. He held prose to a standard, and he was open about wanting his own writing to serve the reader rather than the writer's ego.

Keep a Usage Dictionary Close

Wallace was a real word collector. He kept a running file of new words and circled unfamiliar ones in his American Heritage Dictionary, a copy that now sits in his archive with hundreds of words marked. He pushed his students toward reference books, and toward a good dictionary of usage above all.

A usage dictionary is one of the great bathroom books of all time.

David Foster Wallace, Quack This Way

For the daily habits behind the advice, see the full David Foster Wallace writing routine.

What You Can Steal