Its a good idea to first find where your customers hang out. Generally this would be at a handful of forums. The next step is to hang at those forums and mingle

Its a good idea to first find where your customers hang out. Generally this would be at a handful of forums. The next step is to hang at those forums and mingle with the community. After a while you can approach people directly or start a forum thread talking about your idea and to get feedback on whether people would find it useful.