My girlfriend and I enjoy developing my D&D world a lot. We spend much time talking about what the backgrounds of characters are, how history has developed, what the relations between the different kingdoms and peoples are, what the hidden agendas of the villains are. Her ideas have enriched and improved my world a lot.
At the same time, I'm running a campaign in this world for a couple of friends that she isn't part of (for logistic reasons, long distance relationship). But eventually, we'll move together, and I don't want to miss out on GMing, neither do I want to miss out on developing the world together, and it would be great to finally be able to play together. This leads me to my question:
Can we both be GMs together? How do we split the tasks a GM faces in a session? We're fine with developing the world and the campaign together, but how would we play out an NPC's dialogue with a player? How to agree on DCs and skill checks? And so on, and so on.
Could we take turns? (E.g. every session, or every hour?) But won't one of us be bored, having nothing to do? We can't really take up another player, because we know all the GM secrets, making it hard not to meta-game. Or could we divide up rooms, regions and NPCs amongst the two of us?
Best Answer
There are lots of ways to do this, and some experimentation will be necessary to find the ways that work best for you.
An obvious strategy to start with is to have one person playing the NPCs and monsters, and the other doing the game mechanics. I've done this myself, and seen others doing it, both helping a GM who's very talented at plots and acting, but a bit vague on game system mechanics. In both cases, the game mechanics assistant was playing a PC, and had no privileged information about the world or the plot, but your situation is a bit different.
You might well trade the two GM roles according to which NPCs are going to be involved, since it will be easier to play them consistently if the same GM always plays a particular NPC. This will allow you to have NPCs arguing with each other convincingly, which is rather hard for a single GM.
For example, Alice and Bob are your two co-GMs, and Charlie, Dave and Eva are the players.
Alice might be the usual mechanics GM, and Bob the role-playing GM, but Alice would have some NPCs that were always hers, and Bob might take over mechanics duties when they were centre stage.
If the party split in two, one GM could handle each part, which does make many kinds of tactics for the players easier to run.
In scenes that were just large fights, Alice and Bob could take separate groups of opponents. They would have slightly worse coordination than is commonly the case with a single GM, but that would actually be realistic: coordination in fights is hard.