Approach it like a VC. Identify smart people. Hang around where they hang, like accelerators and coworking spaces. Listen to their pitch and ask yourself whether this could be an amazing thing.

I actually missed out on lots of good companies. Most are very humble. They don't smell like a big shot CEO, more like a lost student. They don't convince you that they're good at what they do, nor do they beg for help. So it's easy to miss. It's just some folks working out of a cheap area of town, sometimes even a large house. I rarely see big startups emerge from the expensive part of town, but there may be exceptions for some towns.