Hardest lesson, huh? Hmm... I'm not sure, but the right mix of "being in charge" and "we're all friends" while running things. While we're all good friends who've known each other for years, I had to balance being "in charge" with that. That is, I'm responsible for pacing, for moving the game along, for running the game, spurring the slower players (or usually, more thoughtful), and the like. It took me a long time to not get all... boss-like, about it. But I'm better now.
1) Learning how to best deal with problem players.
2) Admitting defeat with regards to trying to fit a square peg (problem player) in a round hole (a group with good chemistry and a coherent creative agenda).
3) Adeptly and gracefully dismissing said problem player with the least amount of hurt feelings possible.
Can't XP, but this is a tough one that I don't have mastered (not much experience). It feels even worse for me when that one guy isn't even that much of a "problem player" in the normal sense, he just doesn't really fit into the group (I've had a player that was a good friend of my brother, but he was just too quiet/passive to really fit into our game). Hard dealing with this kind of situation with grace, from my limited experience. As always, play what you like
A variant of this. I used to spend huge amounts of time doing game prep, down to minute detail of each monster and NPC (in any game system I was running, not just D&D). It took a long, long time for me to realize that the players generally did not notice, or care, about the level of detail in my prep - that my rough sketches of encounters were just as good from their point of view, and that the extra detail tended to force me into lines of thought, while having rough sketches left me more open to allowing the players to do cool stuff they thought of in the heat of the moment.
Most of the time, I don't even have encounters prepared (I just wing almost everything), and my players certainly don't seem to mind at all. However, every once in a while, I'll write up creatures, including a weakness or something, and let them look at the sheet afterwards. A couple of times they've found the weakness and used it (once was almost a complete guess), and man did they feel proud of themselves for getting through the encounter. So, I sometimes like to write stuff out, just so that they know how well they did, but most of the time, yeah, it doesn't turn out much different than if I just made it up as I went along. As always, play what you like
