I'll add to the list!
No surprises.
That is to say, very few of us handle change with nearly the amount of grace we ought. If you're going to change something on your game that has been established in the past, give warning and explain why. You're going to get grumbles, that's a given. But the grumbles about warning are significantly less of a heartburn than the explosions of HATE and FEAR that happen when the sky is suddenly orange instead of blue.
Leave yourself room to change your mind.
You aren't going to be perfect. If you make a decision that turns out wrong, then for fuck's sake, reverse the damn thing. Acknowledge you made the mistake, figure out how to avoid it in the future (if possible), and follow through on explaining the situation to the game as a whole. A mistake is only a Problem if you make it a second time out of carelessness and lack of attention to fixing it the first.
Be the change you want to see in the world (tm).
You're the only one you can control, natch. The atmosphere, levels of adaptability, agreeableness, and general tone of your game start with you. It doesn't end there, of course. There are a bunch of people involved. But if the core doesn't hold, the rest of it will falter in due time. Be the player that you want other players to be; expect it of yourself and of everyone around you, even and especially the friends you'd normally give a pass. Even if you're upset, even if someone else is treating you shabbily, you're the center. Own it and it'll ripple outwards from you.
Recognize that you're not on the game to be or make friends.
That's not to say you shouldn't be friendly, or that you have to give up the relationships that you've built over the years. On a scale of -1 (hatred and loathing) to +10 (besties 4 eva), it means you need to treat the players on your game at a +3 minimum (courteous distance). You don't get to have extremely negative scale interactions, and the moment you do, you need to consider asking them to leave. You also don't get to have extremely positive scale interactions with a select few, because the moment you do, you're playing favorites and the other players will feel it and react with resentment. Headwizzing requires a certain level of detachment. I don't personally think that's a bad thing. If your friends can't handle the fact that talking to you as Headwiz is potentially different than talking to you as their buddy, then that friendship isn't nearly as true as one hopes.
Find your peers.
We are none of us great in a void. We are none of us great without feedback. Find the people who aren't afraid to tell you when you're screwing up. Find the people who aren't invested to a creepy degree in their character, who are willing to look at the game from a proverbially global perspective and give you opinions you can consider. You might go your own route anyway, but you do need to listen and consider first. Yours may be the final say, but that doesn't mean making decisions in a vacuum is a good idea.
ES