Plenty of games will tell you what you need to do as a GM, but one thing Vincent and Meguey Baker’s Apocalypse World does really well, is codify those tasks into your agenda and your principles.
Apocalypse World says this about your agenda:
Everything you say, you should do it to accomplish [your agenda], and no other.
Your agenda is a set of a few (in this case, three) things that direct your play. The agenda in Apocalypse World is:
- Make Apocalypse World seem real.
- Make the players’ characters’ lives not boring.
- Play to find out what happens.
Under this, you have a set of principles, whose purpose is to direct play at that mid-level. The book says:
Whenever someone turns and looks to you to say something, always say what the principles demand.
Your principles are a set of broad play techniques and patterns that you can use to make the game run a certain way, in pursuit of the agenda. For example, one of your principles is ask provocative questions and build on the answers. Which will obviously make the world seem real, and also is part of that whole playing-to-find-out thing we’re all interested in these days.
Now this is a pretty cool tool: it means you can tell the GM what they should be doing at a high level (the agenda), and then tie that to mid- to low-level actions they should take to ensure that the game flows in that direction (the principles)1. You can see its influence in a lot of modern story-games - see for example Blades in the Dark and its derivatives, which take a lot of that guidance even as they diverge from move-based play.