Put forth a compelling view of what the future could look like once your idea has been realized. Don’t just pitch this vision — evangelize it and bring early supporters on-board. Attract others by convincing prominent or powerful people to join your calling.
Then create a platform — physical or virtual — that allows these supporters to connect and further disseminate your idea. Find ways for people to link up with, work with, and draw strength from each other. This will help build your fan base to gain critical mass.