I've never caught the full lyrics before, but I've never thought it was meant as a guide in any way. Rather, it's a condemnation of mass modern life and complacency, people getting older and more boring and going through their lives like cattle until they die. It's mocking all the life advice our boring parents gave us when we were growing up. This is all delivered in a monotone, almost robotic text-to-speech voice with Radiohead's typical eerie music backing it.

(As a longtime fan I'm a bit biased, but I think it's worth a listen to understand the tone: https://www.youtube.com/watch?v=O4SzvsMFaek . The rest of the album also adds some context, as others have noted.)