How much, and what kind of, advance planning is appropriate for a sandbox campaign?

Question

New GM attemping to get ideas for a campaign down something similar to a tabletop fallout game.

How much info is too much info for general prep? Can there ever be too much? Or is there a general balance between the GM's plans and the PC's being PC's. Level differences aren't too big a deal in the game I'm running (All Flesh Must be Eaten) but they can happen. Do I want to specify everything in the room and say how things are meant to be used if they find them? or allow more creativity on their part.

eg: Going with an "If it's reasonable for it to be there approach let it be there" or "I didn't say specifically anything interactable was there, so you can't use it."

Answer 1

I'd suggest to use monster types/appearances as indicators of where the PCs are. Terrain can be useful, especially if you make it appropriate to the monsters, but the players will tend to focus more when you're describing stuff that's threatening or fighting them.

In my largest (fantasy) sandbox, I had a safe area in the middle, then surrounded it with loosely defined areas. I made the areas clearer by having different monsters and different dangers in them, as well as different types of interesting diversions (dungeons etc.). I had NPCs explain how different areas were more dangerous, and the PCs were quick to learn where they were safe, and where they were screwed.

Translating that to your game, I'd suggest coming up with a common link connecting all the zombies in one area (say, a hospital) by giving them similar appearances. Also, have the types of useful stuff found be connected to the area (medicine in hospitals, food in supermarkets, petrol at petrol stations, etc.) to help lead them towards whatever they're looking for. Fill in one or two interesting locations (including enemies) per area, then leave it at that. Too much planning is a waste of time, unless you can guarantee that the PCs will go through the encounter(s), unlikely in a sandbox game. Once your areas are done and put on a map, you should be nearly finished.

Lastly, make a series of descriptions of each area (cover all 5 senses) so that if the PCs enter a warehouse, they "smell the sickly stench of rotting flowers [...] the taste of decay is in the air as they feel the slimy fronds". Make the descriptions tell the players a little about their area. Reread them, and see if you can picture the place in your mind.

Answer 2

Prep Amount

Can there be too much prep? Absolutely. Too much info becomes a pain to navigate - you have to scan through your notes to find the stuff that's relevant.

If you invest too much time into some things, you find yourself "protecting" them, that is, either an event or thing becomes something you block the players from avoiding, working around, or affecting because it might destroy hours of prep time, rather than letting it be fuel for play.

Instead, ask yourself:

• What notes do I need to inspire myself in the moment?
• What mechanical bits are easy for me to improvise depending on the system?
• What mechanical bits are easy for me to simply reference (monster stats, etc.)
• Are these notes going to be useful repeatedly, or just for one time? How can I reduce the one-time notes in favor of reusable ones?
• How much can players effectively "go through" in a single session? Can I prep just enough to meet that, and do more later?

GM Plans vs. Sandbox

"Is there a general balance between the DM's plans and the PC's being PC's?" Well, most sandbox games I know don't have a lot of GM plans involved. There may be events going on within the setting, but they are often things that can be changed or affected by player actions.

The RPG Apocalypse World has a pretty good way of dealing with this... you write down a potential source of conflict ("The dam is cracking.") and then you list what will happen, over time, if no one does anything about it. ("The valley will flood.") and part of it is that the rules demand you give steps/signs of forewarning so the players at least know a problem is out there to be fixed. (Mind you, they may end up convincing or getting NPCs to go deal with some of these problems, but the players have to have a hand in making that happen.)

What generally makes more sense for me, in a sandbox game, is instead of producing a lot of "this will happen" type plans, is to simply lay out where major characters or groups are, what their needs/motivations are, and to play them the same way players play their PCs - you know what they're about, so it's easy to improvise.

Did the PCs blow up a warehouse of supplies? All the local groups are now scavenging or fighting over these kinds of supplies. Did one of the PCs leak crucial information about another group being vulnerable? Bandits from a rival group rush through and raid them for their belongings. Did the players save a town, time and time again from danger? They're either out and out friendly to them, or there's a political divide as the PCs have gotten "too popular" compared to the folks in charge.

In this way, you don't have to make too many plans, you just make personalities and needs and react to what the players do.