Several times now, I've come across GM advice on the importance of leading questions. The problem such questions aren't meant to address is that we sometimes want players to contribute to the fiction, and they’re not always sure how to do that. The solution some GMs have struck upon is to ask questions that guide their players toward a playable response. So instead of asking a player how the NPC bartender feels about their character, the GM asks something more pointed: “What happened in your past to make the bartender hate your guts.”
“Leading question,” in that sense, has become a veritable term of art in GMing, but what we’re looking for generally aren’t leading questions in the popular sense. Leading questions are what lawyers ask witnesses when they already know the answer and want it entered into the record. Sometimes, they're used to surreptitiously suggest what the witness ought to say, as opposed to what they would say on their own, much to the judge's ire.
Hopefully, that's not what most GMs are after. We may have an idea of what a player could answer, and their actual answer may even match that expectation. But if the questions we're asking are genuinely leading, then the GM is still dictating the fiction, just behind the guise of involving the players. In such cases, everyone's better off dispensing with the pretense that the broader fiction is, in any meaningful sense, collaborative.
Nevertheless, asking well-calibrated questions can be a good strategy for nudging players to shape the world beyond their characters. Understanding why is essential for figuring out how to.
Why are some players reluctant to contribute ideas about the world of the game? The range of possible reasons is broad, but often it’s simply that they’re not sure about the state of the fiction they’re being asked to shape. The GM is given general charge over worldbuilding, and will typically have a more substantial — and often underplayed — conception of the setting. As a result, players aren’t always sure what additions would makes sense. The question cedes some of the GM's authority to the player, but they don't necessarily feel competent to exercise that authority. What we need, then, is a question that nudges them not toward any particular answer, but into a position where they feel competent to give a good answer.
The NPC bartender for whom they're being asked to improvise a backstory was introduced only moments ago and is still just an abstraction to them. “Why does the bartender hate you?” is a stronger prompt than “Tell me about the bartender” precisely because it adds to their information about the state of the fiction. That, in turn, gives the player a bit more expertise about the world, which is something they can build on. They can build on it not only because it gives them a better command of the state of the fiction, but also because it relates the fiction back to their characters, which is the part of the game over which the rules give them the most authority.