[cgulovsen]

It really depends on the situation. In a recent endeavor, I took to sites like Quora, Reddit, HN, and I went outside and talked to people on the street.

It's all about asking relevant questions that open ended and not biased. In the recent experience I had validating an idea, I ended up getting great nuggets of information that helped us tailor our app to address the pain points users found in existing products. It's also important to note here that this doesn't mean that you're guaranteed money; all you have done at this point is understand that the issues exist and that you (hopefully) have a solution. Hope this helps!