Henry
Autoexreginated
Expand on that thought, please. I've always found that most RPGs play very well having the players affect the game world through their characters.
Expanding on that, alot of the time when a player asks for or about something, the question that they ask is really standing for some other implicit question.
For example, if the player asks, "Is their a mage guild in town?", the real implicit question is usually, "Is their a wizard around I can talk to?"...
You don't have to say 'Yes' to everything, and you can easily ruin a game by saying 'Yes' to everything just as you can ruin one by saying 'No'.
I'll give a more explicit example.
In a D&D game I played in over 15 years ago, I was playing a swashbuckler type character in a DM-original game world. I asked if I could design some of the details of the city I came from; he gave the go-ahead, and I envisioned a cross between a renaissance port city / early-enlightenment type city, with a city guard inspired by the Muskateers, with a more fantasy feel, complete with major stores, points of interest, etc. He took it, made some changes to what I'd given him, let me know the parts that he changed that my character WOULD have known (there's a statute of a horse in the bazaar, not a gorgon, that sort of thing) and we ran with it.
I helped the DM create a part of his world, and when we visited the city, I knew more about it than the other players did, just as if my character had actually grown up there.
I'm not saying every player has that kind of dedication or sheer nerdiness, but it applies in a lesser extent, too. If the player wanted to shop for a "fiery-tempered coal-black destrier that made most people afraid of it," so he could tame it and basically ride a mortal hell-horse that scared most everyone but him, then I say let him find it. Give him the (reasonably doable) checks to tame the thing, and let him have fun with the occasional peasant that gets too close and gets his ear nipped or such. The player gets his "moment of cool", and you've added something to the game other than "No, you don't find such a horse. You do find a serviceable steed, and get moving on." or the more punitive, "No, all this town has is a broken down nag that the children laugh at when you ride through town." Who is either of those helping? No one at the table, in my opinion.
So, the "Wizard's Guild" example comes back to, "Yes, AND" the characters have a connection to the town that they didn't have before, you have an example of a non-combat experience you can expand on, and your game world has a half-dozen or so new NPCs that you never thought of before now. Win-win all around, in my opinion.