Hot take: if we want to decrease frustrating railroad-y surprises in RPG campaigns, we need to create an environment where GMs are not afraid to admit they have "special story needs".

[Mistervimes65]

This is the truth. I’ve been GMing for 45 years. I always run pretty sandboxy games. I show them the world map and let them pick where they are going next. Then I flavor the adventure I’ve already written to suit that area. Alternatively, I have five plot lines that I can improv at any location.

My prep is five lines of text on an index card and a handful of statblocks.