Think about why you're doing what you're doing. What kind of problem it solves? Who has this problem? Once you understand the problem it takes some trial-and-error to find actual people that have it. The good thing if you're right about the problem people will be willing to talk to you, since you might have a solution they are looking for.
it takes time to really learn your users. I've built a community site for developers (DOU.ua) and it took me five years to figure out the most pressing problem my customers have. May be I wasn't listening hard enough but it still takes time.