questions bring your world to life, but all of those details are wasted if you can't answer the most important question in any game: why do the players care? What is at stake if they fail? Succeed? It's not enough to threaten the city, the kingdom, or the world with a tough monster. Stacking loot for the sake of stacking loot feels incredibly purposeless. Deciding the fate of a cursed child won't have any gravity if there isn't some tangible connection that player's feel.
When players care about the in-game situation, they make decisions. They drive the narrative. The opposite is also true: players who don't care about the in-game situation still make decisions. They ignore the GMs bait and keep fishing for something else. They take off in a totally unexpected direction. Whatever their decision, they are steering the ship.
Having read entirely too many forums and blogs related to gaming, one of the biggest fears that GMs seem to have is the players choosing to go off in a direction that was unanticipated. This is the problem of having a story that you want to tell. A bad GM reacts to this situation by railroading; a good one, rolling with the punches and improvising.
A whole other style of game, the sandbox, seeks to remedy this problem by presenting several hooks and letting the players bite the juiciest one. Not only is this style of game a lot of work (you're preparing multiple plots), I don't know that it fundamentally solves the problem of the GM having a story he or she wants to tell. While it certainly engenders more player choice, I'm not sure the amount of work it requires pays is worth it.
However, as I said, these actions and decisions cannot exist in a vacuum. They have to take place somewhere, populated by the illusions of living, breathing people (or demi-people). Rather than labor over one or several stories for your players, why not step back before any characters have been made and talk about the kind of game you all want to play?
At the beginning of this post I posited that the single most important question you need to answer is why the players care. This is by far the easiest way to answer that question. Give them a say in building the setting, the major conflicts, the immediate situation at hand. Let them incorporate relationships to the people they are saving or protecting. Let them make their own purpose, and then challenge them to fulfill it.