Anything that says the DM should work more (versus good advice, which tells them how to do more with less time).
Back in ye olden days, this meant a bias for home-brewing over using modules, as they were called (even though there were excellent modules available, and people played them). Later it might mean creating an elaborate sandbox, or really trying to understand your players and going out of your way to cater to your players (though this can bog the campaign down and, in various ways, actually annoy those players).
There are other examples, many, of "here is all the extra work you can do to be a better DM".