If you don't know what's good, buy what's weird.
I mean, obviously, "find out what's good" should be a preliminary step when possible. But this came up when timprov and I were discussing my theories of buying beer for other people's consumption, since I am a non-beer-drinker. I get things I recognize markgritter as having bought before. But if I'm looking for variety for a party and don't recognize enough stuff as good, I grab something that looks totally off-the-wall, on the theory that drinking bad or mediocre beer they've never had before is at least going to be a data point for people, whereas drinking very familiar bad or mediocre beer is just depressing and pointless.
For what things does this not work? (Note: this is not rhetoric proclaiming, "This works for everything!" It's a genuine question.)