There's an entirely legitimate question here behind this quip. I don't think there's a magical answer, but one approach I've found is to try to be a mini exper

There's an entirely legitimate question here behind this quip. I don't think there's a magical answer, but one approach I've found is to try to be a mini expert in a tiny, tiny slice of a bigger area (usually bridging over knowledge from some adjacent area I know). This means that I can then evaluate those who talk about this tiny area, and get a good baysian guess as to there broader expertise from there.