What has really worked for my co-founder and me is to talk to potential customers. Basically, once we start asking questions, our potential customers inevitably

What has really worked for my co-founder and me is to talk to potential customers. Basically, once we start asking questions, our potential customers inevitably start saying things like, "Well, we tried this company...." or "Have you heard about this other company...." I think this yields great up-to-date information. Sometimes directories can be horribly out of date and irrelevant.