How many times do you read through various RPG forum posts to see some pillow biting, bedwetting Player crying about how it's "not fair" that a DM/GM imposed a rule in the game which didn't go the way the player wanted? Now the DM is being talked about as if he or she is a criminal who ruined the game because they wouldn't allow the Player to do something utterly stupid and out of bounds that would throw the game off but it would make the player feel better about themselves?
There are a lot of those out there.
At the same time, there are some dandy posts by DM/GM's who seem to think they are running a gulag instead of a game.
There are quite a few of these too.
First of all, it's a game people. A fantasy game. Get over it.
Secondly, It's a game with rules and archtypes. Play the game and don't make others live or die over the small stuff.
Players, the game takes place in place X, you all came together to have an adventure. The DM (probably) worked for long hours to either write that game or get to know it in depth if it's a published module. If he or she says the beginning of the adventure begins by the party arriving in town Y and that they see something at building Z or Tavern A, then that's where you go. Don't suddenly decide you want to turn around and have your character go in the opposite direction then cry that the DM is "railroading" the game. Don't be such a pansy
DM, place the setting on the stage and be ready for the Players to go through the setting as they will, as long as they are going through it, all is cool. If you try to hold their hands and walk them through it of force them into a specific situation, don't be surprised when they all have to leave early to go wash their feet. That is "railroading" when you don't let them go through the adventure on their own.
Players, you chose a Class that is associated with requiring a connection to a deity of some sort (Cleric, Druid, Paladin, etc...). Don't be stupid and think that there aren't going to be some added conditions and stipulations for your PC. if you try to do something that the Deity your PC chose to follow and represent does not allow for, don't cry when that spell doesn't work or there is some repercussion for stepping out of bounds of the Deity's expectations.
DM's, just because you get to "play god" doesn't mean you get to just invent crap on the spot because you're jealous the player thought of something you didn't expect. If it's a known deity, both you and the player should have gotten together up front to make sure you both know what kind of deity it is and the expectations of that deity. If it's a deity you or the player made up, then make sure the both of you sit down and flesh it out before game time so that both of you are on the same page going in. There really shouldn't be surprises mid game because you want to spice things up out of the blue.
This isn't a game that is supposed to a historical simulation and it isn't a game that must be a duplicate "real" world.
Hell, even the the game's author tells you at multiple points across several books that if it breaks the game for you and your players, to ditch the book rules and go with something that works better for your group.
Yes, most people expect rules, even if they don't follow "reality", to at least make sense. If a rule comes up and it doesn't make sense to you as a DM and the Players, then by golly, change that rule. This is your game, not some nameless twit on the internet who declares that you are evilspawn if you dare wander off the words on the printed page. That's some nerd with no social skills and no social life. Ignore them for what they are and play the game that works best for your table.
Players, learn to appreciate what you have. Chances are, if you're sitting down to play a 2 or 3 hour adventure all you had to do is roll up a PC and bring your imagination and maybe some dice.
For those 2 or 3 hours you play, it is most likely the DM had to spend double that amount of time and likely even longer (especially if they are writing the adventure themselves) just so you would have a game to play.
Just as you want to be creative and come up with new, imaginative ways to handle situations in game, so must your DM have to be able to make adjudications and rulings on the spot for that new move or new weapon, magic item, etc... on the spot. Give them a break. You don't like DM fiat to determine a result? Then make sure you aren't putting the DM into a corner where they haven't had the time or opportunity to plan ahead and know what to do if that situation should come up. The game must go on and so the DM has to make a ruling quickly. Sometimes that means making it up then and there so as to keep things going. Deal with it. Move on.
One thing that all of the books agree on and is repeated multiple times throughout is that the game is the DM's game. They have the last word. Yes, the book does tell DM's that if they run the game by not taking the players into consideration then they run the risk of not having any players. So there is the ultimate last word.
If your DM is being that big of an ass then push back from the table and go do something else. Hell, start your own game and be the DM yourself. See how that works out for you. If that DM wants to DM, he'll change his ways (or hers) if they can't buy a clue even if everyone walks away from them, then they are going to be one seriously lonesome DM.
On the other hand, DM's, if your have a player or more than one player who expects you to hand over everything and cave in to their whining and tantrums, then kick their sorry away from your table. Most likely, the other players will appreciate you having the intestinal fortitude for owning your game and for making sure that everyone at the table is having fun instead of just some little "that ain't fair" nerds who aren't happy until everyone else is miserable.