So it's been said elsewhere that when the stars align such that the GM is "responsible for the fun" (i.e. everyone else can be jerks but the GM has to somehow turn the game into something great) that something bad is happening.
But... there's another thing, which is ardently trying to make a game fun for everyone.
That's what I want to do.
I don't want to talk about my players specifically, but let's assume Geek Social Fallacies don't apply. I'm pulling in a mix of people, a mix of ages, and while I'm getting a mix of styles, everyone is conversant enough in what they like to know that they legitimately want to play my game. I run a game where we play to find out what happens and there aren't very many rules.
I've got their character sheets, with a how they deal with problems, relationships with at least 3 NPCs, how they relate to other player characters, and how they are likely to get themselves into trouble. So a pretty good starting point. Now, given that I have all this, what should I do to delight my players?
Another way of putting it:
How do I go from a good R-map, meaty character descriptions, and some color, to delighting my players?