research hacking - for those of you that have naturally hacker mentalities

Hi all!
Given some of the amazing ideas folks here routinely come up with I was hoping to pick the collective brain with this question:

I'm conceptualising (before a write code) an application that will help restaurants/cafes etc promote their best offering (menu item, for example) to patrons. What are some of the clever ways of researching this problem, collecting data and validating before building?

Of course, this question is looking for answers beyond "interview/ask them" as i'm already doing that!

Would love to see what others come up with, as i think this is a re-usable topic.

thanks!