First, it takes 32 owners to make a good world. Now, to answer your question.
1. Figure out what you want from a world. Some people want competition, others want to build 125 win teams and are willing to let everyone else worry about being competitive. Some want defined guidelines for trading, some are "It's your team, do what you want." Some think maintaining minor league pitching staffs is of the utmost importance, others think "More AB for my hitters!" Once you figure it out, make some reasonable, simple rules to make it happen. And enforce them if/when the time comes.
2. Populate the world with owners who want similar things. They don't have to be 100% with you but they need to to be willing to play within the guidelines and help enforce the rules(with a veto if it's a trade rule).
3. Start finding replacement owners outlined in #2 BEFORE you need them. Commishes who wait til the last minute will be pressured by other owners to "Just take the next guy who asks to join so we can play." That goes back to my first statement. It takes 32 owners to make a good world but just one to F it up. Screening is key.
4. Put the well-being of the world ahead of your team. That doesn't mean you can't make your team better, it just means if you're offered a deal that you know is stupid, that you shouldn't be taking it. Treat everyone the same even if they annoy the hell out of you. Fair but firm!
Reflecting back, I think I'd keep #3 to myself. I think that gives me an advantage over most commissioners.