Spend only a little time each time you work on it.
Decouple the effort from any other existing commitments and projects.
Seek potential for useful value in about three years. The project works when having one of something has little value, but having 1000 or 5000 of them has plenty of value. Realize that it might take more time than you plan to make it happen.
Note things that are happening across a border or around the world, not just here.
Identify sources of leverage, where a complex current process can be simplified.
Consider that tools tend to attract tool-wielding people, and problems that require tools to attack.
note: edited 10/27/10 to make it make a little more sense.