What are some ways to create emergent narrative in a world building project, or in a writer's workshop?

Something that really strikes me is that the best parts of the world I worked on with my collaborator (my wife) are the parts that we didn't deliberately create. These are the details that emerged as we wrote the story, mostly through trial and error. The parts that we intended to be a certain way are often less mature. So far I haven't encountered a reliable way to manufacture this process with long-term collaborators.<br><br>How do world builders either do it solo, or in a collaboration, such that the project feels dynamic, vivid, lived-in, and substantial?