There are a few questions which are so useful to running games that they often go without saying. The pair I view at the heart of this are "What do you want?" and "What are you going to do?". These are questions too the player from the the GM, even if never explicitly asked, but they're also a challenge to the GM in that she must know these questions will be asked and must be answered. What response that demands depends upon the GM and the game, and that difference can be quite telling.
"What do you want?" is an interesting question, in large part because it is directed at that player. This may seem straightforward, but it gets interestingly muddled when one starts taking into account the reality of the character being played. Many gamers would choose to focus on what the character wants as the important thing, and they would sometimes be right to do so, but probably not for the reasons they think. In those cases, the thing the character wants is what the player wants, so everything's copacetic.
But it's important that the focus of the question stay on the player because those two things can occasionally diverge. The most obvious example of this is when the player wants to see the character fail, but that can be a rough distinction to make to a player unfamiliar with the idea. To clarify, it can be helpful to look at the discrepancy between the motives of the player and character, even if their goals are identical. While Bob the Barbarian might want to kill the dark overlord to avenge his family, Bob's player wants to do it because it will be an awesome fight (and there will also be fat loot and XP).
Of course, it's easy to say that at a remove, but the reality is always more muddled. Sometimes the divide is small enough to be near nonexistent. Bob may hate the Dark Lord for the things he's done, and Bob's player may also hate the Dark Lord because the GM has made sure he's hateable. The subtle distinction between these motives will get overwhelmed in the sheer enthusiasm to take the guy's head off. And that's a good thing.
From a player's perspective, this distinction is almost trivially unimportant. The player wants what he wants, and will generally pursue it rather than describe it. This can cause some confusion for others or frustration for the player, but that's a natural part of such things. And, barring a particular sort of approach, it's the GM's problem.
For the GM, it's a fascinating problem. Sometimes you have clear pointers to what the player wants, either through long familiarity, clear communication or a game that includes clear flags in the system. But more often than not, you're left faking it as best you can, hunting for clues, reading responses, and going forward as best you can. And that's fine - it's what you signed up for. But there's one last twist of human nature to deal with: We don't always know what we want.
In many ways, the GM's role ends up being like that of a chef (and for purposes of argument, we will assume you are all _excellent_ chefs). Diners may order meals with varying degrees of specificity, from precisely detailed to open ended trust of what the chef recommends. A chef loves it when the trust is high, and tries to reward that with an amazing, unexpected experience of things you would never have thought to order for yourself. There are risks - sometimes the sweetbreads just don't work for you - but the rewards are equally fantastic. But sometimes you just want a burger. That's not always a bad thing. Sometimes a burger is what you want. Sometimes your tired and want comfort food.
But it's possible you're that guy who must have his order just a smidge over medium, with onion and two slices of tomato, mayo on the bun but mustard and ketchup on the side, no sesame seeds and can you substitute the fries with a side salad? With spinach or romaine, none of that iceberg crap. And of course, you'll salt it before you taste it, and send it back to the kitchen at least twice.
If you're that guy, it might be worth remembering that you can get away with that in a restaurant because you're paying for the privilege. If you think you are entitled to the same in your gaming,then I might ask you to reconsider the possibility that even though you know you really like your burger in exactly that way, that it's possible there are other good foods out in the world, waiting for you to try. Even if you don't want to go too far outside your comfort zone, consider the possibility that the chef might change something because he thinks you'll like the change, and he's making that decision based on experience and knowledge. You don't need to jump right to the sheep's eyeballs, but maybe you could consider the lamb burger.
Just a thought.
1 - When players embrace the distinction between what they want and what their character wants, they change the game up. Like any change, this can be for good or ill, and like many changes, responses to it are likely to be entirely visceral. To one group, this may mean embracing a stronger narrative, but to another it might appear to be shameless metagaming.