Having played RPGs for the better part of 28 years now (wow....), and having run about a dozen long running campaigns (one upwards of 20 years, but mostly active for about 15, the others in the 0.5 - 4 year range, not counting piles of little died-a-borning versions), I think I've developed some insights into Game Mastering.
So I'm going to do a series of brief musings on things I've learned along the way.
Lesson 1 - Play What Motivates You
The GM is the person with the most invested (emotionally, financially, and temporally) in any campaign. He has to be to spend the time required to put on a good campaign. If his interest wanes or his will falters, the campaign may well collapse.
The GM has to want to spent easily 200% extra time over and above playing the game to work on events, to track things that happened, to supervise book-keeping, etc. Of course, you can cut that if you use a pre-written story arc in some modules, but even then you'd better spend time familiarizing yourself with the material, the enemies, etc.
Players can show up without a character sheet, without dice, be half asleep (or entirely asleep if they are a Bugbear) at the table, and the GM is supposed to handle these situations without batting an eyelash. The GM, on the other hand, had better not show up groggy, unprepared, without dice, without his modules, etc. or there will be a ruckus.
So on the GM falls the larger part of the burden. I'm not saying that a campaign can work without motivated and involved players. It can't. The players are critical to the success of the campaign and if they are into the game, it is far more fun for everyone including the GM. But the GM has to be as into it and commit more time and effort.
So, the GM has to love the game he's putting on. He may not love everything about it (GMs never do - they think they could always do it better, differently, or in some more exciting fashion or they have this or that gripe with the rules, often tweaking to remedy the supposed flaws). But he has to, overall, love the game.
My observation has been that I always end up GMing the sorts of games I would want to play in. I think that is true of most GMs, allowing for a certain amount of flexibility to accomodate some of the wishes of the players.
So, GMs will end up running games they'd like to play. And that is mostly a good thing as long as it is not taken to extremes. It's a necessary thing to maintain the enthusiasm and the work session after session, some of which are guaranteed not to come up happily for all and not everyone is a home run. Some end up triple play blowouts.
The GM will always see his world more clearly and be more interested in it than his players. This is not to say the players will not be interested or cannot grasp some of what the GM is trying to convey to them, but the image can never be transferred whole cloth.
The GM's style of running a game is as much derived from this truth as his storyline is. This includes pacing, the role of NPCs and players in the World, how Epic or Gritty the game is, the subject matter of adventures, the sorts of characters he encourages, the sorts of scenes that he sets, and the general tone and flavour of everything in the game.
If the GM likes Space Opera, you may get a dose of Star Wars or Dune. If he like something pulpier with a common touch, you may get Serenity. If he enjoys huge empires and little people in them, you might get Traveller. If he likes high fantasy, Lord of the Rings might make sense, or Elric. If he likes rules crunchy fantasy that has a familiarity to everyone, you'll get some flavour of D&D. And so on.
The game sessions can be languid crawls with a lot of emphasis on the minutae of tasks like bargaining with a merchant for a new water skin or how the players are going to pack their backpacks. The games can be frenzied and somewhat forced chapters where the GM wants to get through encounters at a certain pre-conceived rate. The games can feature many side chats or those may be forbidden to speed up play and maintain focus.
The game can have frequent casualties or few to none. Advancement may be swift or glacial. The game can be realistic or fantastic, encouraging either sensible choices or exciting and cinematic ones.
All of this will be derived form the sort of game that the GM wants to play, how the GM sees PCs and NPCs, and so on. And this all ends up being the best experience when the GM loves what he is doing.
When he loves what he is doing, a GM can convey some of that emotional truth through the narrative. His players will sense his love for the material and his interest in it. ideally, they'll also sense his engagement with them and his interest in their goals within his world.
So, Lesson One: Run What You Love. Play What Motivates You. It might or might not work out, there are no guarantees, but it is more likely to succeed than any other alternative.