1) Start it yourself, and be prepared to do it yourself. This doesn’t mean you will be doing everything yourself, and it doesn’t mean you can’t give things to other people. It means that if you don’t have anyone else to do something, you have to be prepared to do it yourself.
2) Get something working, even if it’s simple and sucks, as quickly as possible. If you have something that works and sucks, you’ll want to improve it and make it suck less, which is good motivation.
3) Get users as quickly as possible, and if they want to help, let them. Make sure you talk to them and tell them about what you’re doing and why.
The way #3 worked out for me was that I got other mudder friends involved pretty much as soon as we were able to build areas online. They built areas, which gave them a creative outlet and helped the game, and I built code, which helped them be creative. They pushed me, and I pushed them. Great motivation.
4) Take good care of your users, and reward them for finding bugs in your stuff. The value of testers and testing cannot be overemphasized.
5) If something needs to get done, sit down and do it. Don’t wait around until you find someone to do what you need done; if other people wanted to do it, they would tell you, and if they do it when they don’t want to, the result will be poor.