From both player's and GM's point of view I've enjoyed most about games where players have lived in one specific location. They get familiar with the people and location, may start to like people there, get possessions or even rule a portion of the area.
Or, would you rather play Human warlord or Lord of Raldwik, Hero of the Three Rivers Battle?
Every GM has her own tools of the trade, little tricks she uses in his games. Sometimes you can just shake things out of your sleeve, but sometimes it's good to have some kind of tool you can use when in doubt. A tool I've used for years is a Luck roll, a simple d6 you roll for the character or group doing something.
Players are often lazy. While they enjoy playing games, they might not share Game Master's enthusiasm to the campaign setting and it's world, and as getting to know it could require reading somewhere from 10 to 150 pages, they might not really know or understand many things that come up during the game.
As our games often go forward fast, that question often comes up. Especially when fighting against enemies that can see in darkness, it can become important. It is often ignored, but it can become an effective combat tactic to get rid of opponent's lights.
One of the most impressive moments I've experienced in a rpg as a player was in Runequest campaign, where my character wanted to learn some more spirit magic, healing this time. The following text tells how the learning was handled - the GM running the game is quite exceptional GM and I've learned a lot from him.
I have way too many game worlds and genres on my 'to-run' list, so I have no hope of running many of them as a campaign. I would't have enough material to run a campaign for many of them anyway, but on the other hand, I wouldn't want to run them as straight one-shots either; Players often want some continuity, so a series of one-shots doesn't sound so good.
I'm most fascinated about an idea of being able to run games for my kid(s) some day. And not just for fun; rpg's work well for educational purposes too. You can use games to teach kids historical facts, lessons about behavior and moral and other useful things while having fun!
When designing or running an adventure, you need to be careful about how you use details. While details can make a story alive, they can also make your players fall asleep.