To me, the ideal is as little as is necessary. If there’s an NPC, they have a name, face, personality and motivation, maybe a generic stat block. If there’s a foreign nation, then it has a name and a two line description at MOST. And if there’s something I find a need that I don’t have, I stall for time until I can fill the gap in properly.

But then, that’s just the ideal. I also go a bit nuts with it if left unattended too long.

“Whatever fits on a flashcard” is my golden rule.

If the players are visiting a new city/town, the city/town gets a POI list and a key NPC list on the card. Each major NPC gets a flashcard. Each special item the players get goes on a flashcard that I can hand them when they receive or find the item.

Granted, I usually have a plaintext markdown doc that sketches out how I’m planning to weave the pieces together for each session, but each piece of the story in that doc? Written on a flashcard.

My preference is to take an established setting and run a game in that. The most prep I did for one of my games was my Dresden Files games set in our home town. I looked into local legends and planned a bunch of character details and motivations.

In general I try to do as little as possible and improvise most things. Usually I’ll have some NPCs or factions with some motivations and plans. Maybe a few thoughts about where the players are heading next.

I’ve come to think of the process of GMing more like stage production than storytelling. You litterally set the stage for your players and you just need to control what’s on that stage at any given moment. So instead of writing out entire cities, towns, dungeons, and deep descriptions I’ll come up with a unique shop or NPC and drop it in when the situation calls for it. Even with a map and set locations, if the players haven’t visited yet then they don’t know what’s there. You can wheel in the set pieces and backdrops as needed. The party doesn’t see the stagehands moving the scenery they just need to enjoy themselves onstage.

It works for me because I might have a fun idea for an NPC or location randomly and write it down. Then I have a catalog of people, places, quests/treasures to pull from as I plan sessions. And if the party doesn’t interact with it that session it goes back on the shelf.

Otherwise I have a loose plan for the overarching main quest but I spend a lot of my time thinking about how the world will look based on the characters choices. Like right now the group failed to stop an assassination of a lord. This also got an ambassador to another nation killed. With tensions already high between the two kingdoms, how will this effect everything else? I found that so much can change in the world based on their choices that planning so far ahead can be detrimental and I’d end up trying to railroad them early on.

I plot out a few thousand years of history for the setting so that there are recognisable strata of cultures in the locations the players explore. I usually tie quests and narratives into the history so that its all meaningful and not just window dressing.

I do usually use an existing setting as a base, preferably one that has some established history to build off, usually Greyhawk.

I generally start small and personal. Let the characters explore one tiny corner of the world, get to know the NPCs and get a feel for the setting. I normally have some idea about the larger world and how this corner fits, but until something is canonized through play, nothing is set in stone. It’s both a world tutorial and gives me a chance to adjust things in response to how the characters interact, their backgrounds, how engaged they are, etc.

How and what to tune is a whole other question, but it’s a shared story and being open to ways to help players feel more invested means it’s a huge waste of time to plan out a lot of things that players never care about or see.

On the other hand, I’ve started in campaigns where a DM spends months planning out a world in great depth and 30 minutes into play I know that it’s all going to fall apart within 3 sessions. I’ve seen other DMs who literally just run group after group through the same world or even story every time, even when it’s the same players, because that’s what they spent months or even years building. It’s dull as fuck and makes me feel like I’m just there to witness the greatness of the DM’s world-building or unwritten novel. That being said, it’s perfectly fine if you view it as a purely social event and don’t get invested in having agency.

Because I am a very creative person, I get great enjoyment out of a high level of world detail in my campaigns. I get really bored with cookie-cutter NPCs and/or just reading and using an existing campaign setting as written. This just isn’t fun for me, and if I’m not having fun, there’s no point to it all. Of course, I know that sometimes life gets in the way and I simply don’t have time to do all the things I want to do. It’s important to know one’s limits and try to just focus on what is fun, what will keep the game flowing and what will be memorable for your players. I tend to focus the most on NPCs - their personalities, mannerisms and goals. And yes, I do all the voices, too. I suck at it, but my players absolutely love it.

I have not done it much because I don’t have the patience. I had a few neat story things but like one superhero one I made everyones characters did their thing in our hometown so like locations and such were easy to map and plan.

This is honestly the approach that’s given me the most peace of mind as I’ve gotten more years of GMing under my belt. As little as possible, but at least something for everything, so I’m never truly caught of guard by player shenanigans.

If I’m world building and not just borrowing, then I go into decent detail. I have a set table of information I try to have fleshed out for every capital city and then another important city in whatever country. So in terms of that, it can get granular.

Cities usually go something like

• Brief history, population, population type
• Government type
• Law level (lax, moderate, authoritarian, etc), literacy level
• City culture
• Important places/holidays/NPCs
• Famous dish
• Intrigue

Some of these are left unanswered if they’re too much, but I generally try to at least get a handle on how strict the law is, how smart the people are, and the culture and food. This helps me get a clear enough image to envelope my players in any one city. I personally also have a lot of fun trying to think of the dishes, ice flowers drizzled with fruit juices in this desert city, while an underground settlement has fried mushrooms and cow beetle steaks.

I also prefer to leave the imagery of a certain city up to an image as that can really inspire me to go from whatever I’m looking at.

Shit, that’s the part of prep that’s fun

Ignoring established world building, which I don’t count as campaign building, I tend to have an overall plan, plus a handful of probable diversions. Each path is going to have NPCs as appropriate, though I tend to keep them as just notes until maybe a couple of sessions before they’re likely to be used.

As an example, I might have “lvl 10 chronomancer; drow, w/magic staff, 1 ring, and familiar” when I rough out the campaign. Once I’m sure the players are going that direction, I’ll pick the specific gear, build the NPC’s spell list, and have a plan for the encounter that includes combat, non combat, and usually a combo of the two. But the encounter plan is all mental, no need for written notes of that kind of thing.

If they’re going to a location I’ve already got on paper, it’s easy prep. But I do have a lot of room that isn’t labeled on the map, as well as locations nobody has gone during play. For those, it’s usually just writing down existing ideas, and cooking up details if there’s a divination or scouting run, or whatever.

It’s one of the benefits of having an established world to play in that’s also huge enough that there’s room to grow. I never have to build from the bottom up, it’s only for one off and/or “non canon” play that I do much of that at this point. So most of the depth of those is in my head anyway, not on paper at all.

Mind you, I still have worlds I haven’t used, and likely never will. It’s a long standing mental hobby. But I really enjoy both depth and breadth for my setting.