Managing a sandbox game can be hard. Although they’re my favorite types of RPG, sandboxes ask a lot of a GM. Unless the GM plans to improvise, sandboxes require that the GM have a great deal of cause-and-effect committed to memory, and portray a broad ensemble of NPCs, each with their own objectives and motivations.
I’m running one sandbox-style game and one theme-park-style game right now, and I’ve borrowed one of the techniques from the theme park game to help me manage my loose ends in the sandbox game. For each NPC the players may encounter, I bullet a few of the most important elements of gameplay that the NPC needs to communicate. Often, these are pieces of information, but they can just as well be personality characteristics or other discoverable actions that the players can reveal.
In much published game material, NPCs are represented by stat blocks and/ or character descriptions. That’s fine and good, but in practice, at the table, I don’t need a bunch of stats unrelated to the interaction at hand, nor do I need a paragraph-formatted character history and profile. I need a concise summary of what the players can discover or do when interacting with that NPC. I can always look up the stat block or re-read the description, but in play, a bulleted list is a very convenient shorthand. The key is to make a note of the items that are immediately important to play.
Since I do so much of my own setting and encounter design instead of using published materials, I often simply create the bullet points themselves, and let the actual personalities emerge from the interactions with the players. Despite the gloriously inefficient nature of roleplaying games, this allows me to direct my attentions to the characters and locations my players find interesting without spending unnecessary effort on people and places that don’t strike their fancy.
Depending on how much of an enthusiast for maps you are, you can use a similar approach to geography. (Robert E. Howard’s initial conception of his fantasy world started with an essay, “The Hyborian Age,” from which a hand-drawn map emerged.) Rather than physical geography, the bullet points can suggest locations and characteristics, allowing for actual play an exploration to fill in, much like character personalities. Too much detail, especially described orally, can harm immersion, so emphasize only the most valuable descriptions. Especially if you handle travel in montage sequences, using bullets gives you potential discoveries or conflicts to encounter, while providing enough detail for supporting the fantasy.
And extending from there, you can apply the bullet-point highlight method to any concept your game seeks to explore. The value of the bullet points is that they can be dropped into the game conversationally, simply as a statement of fact or perception. The lack of detail is the defining feature: As GM, you present the concept in broad strokes, and the details emerge as player interactions give substance to the encounter.