I think that's what a lot of this thread has been about, when not getting sidetracked into arguments about definition and so on.
I'll offer a piece of advice or guidance that I learned more from the narrativist side of the hobby than the trad side... as a GM, make all the dice rolls in the open and share all Target Numbers or Difficulty Classes with the players before rolling. Just put everything out there in the open. Make the entire process transparent to the players. It's far more beneficial to play than keeping things hidden.
Another recent one that's been mentioned (though maybe in slightly different terms) is "the result of a roll should never be 'nothing happens'". I very much agree with this... keep things active and moving. Let things develop rather than staying the same. Otherwise, don't pick up the dice.
Another I really like is from Blades in the Dark, and it is "Keep the meta channel open". Here's what it says below:
When you portray and NPC, tell the players things that are going unsaid. Invite them to ask their gather information questions to dig deeper. The characters have a broad spectrum of senses and intuitions to bring to bear in the fiction; the players have only the narrow channel of your few words. Help them out by sharing what they might suspect, intuit, feel, and predict.
I expect that each of these would meet with resistance from more conservative minded folks, but I think they're great bits of advice from other games that have greatly enhanced by GMing of D&D and similar games.