From what I've seen, there is no exact formula. A big thing seems to be for you to be the newer game in an area that people wish to play in. You can subscribe to every 'this is how to do it best' and still fail. You can also just shoot and pray and get a game that lasts awhile. Honestly, this is the only reason I can imagine that BNW survived as long as it did.
However, from what I can see, the main thing is to make a game with a theme you adore. Then, you have two or three staffers that you trust to help make it. You have to entrust them to make game changing decisions with plot or policy on any given day. No matter how many newsfiles you make, no matter how much you plan, there will be the one asshole who will weasel through all files in order to try and do what they want and they will most likely do it when you - as the head staffer - are not there. If you trust each and every one one of your staffers to make the right call when that thing happens? You're good. If you can trust them to abide by the rules of the game and not be that one asshole who will find loopholes? You're good, too. From what I can tell, a lot of games suffer from inter-admin fighting or a complete disillusion wiht the playerbase and making the game about themselves in order to make their efforts worthwhile.
You need to love the game and the idea, because players will generally suck the life out of you. It's not anyone's fault. Everyone wants their piece of the pie and most players will want to contribute, but there are the few that need to be The Best or Not Understand and it will drain you. So, you need to be all in and realize that they're there because of an idea you created. The art of knowing when to say No is very important.
Honestly? I feel like you won't know how to run the MU* you want to run till you're actually doing it. It's different for every game. But, the main things - to me - is love the subject, be willing to suffer fools, and learn to compromise in a way that makes the majority of people happy but does not sacrifice the vision of the game.