I don’t. For my programming course, I list three books I think would be helpful, and I list them as optional. No one has to buy a book. IMO, professors who can’t teach without a textbook are lazy. You should be able to create your own lessons, notes, presentations, and tests without needing the student to follow along in a book. The worst, by far, are the professors who make their students buy their own text book. That’s just evil and rude and self-serving. I hate professors like that.