If you're interested in a woman, but you get the vibe she isn't in to your physical appearance, grow or shave your beard to the opposite of what you currently have.

It sounds stupid, but trust me it works. If you have a beard, and she isn't into your appearance: shave it. If you don't have a beard and she isn't into your appearance: grow it.

Beards/facial hair drastically change the way you look despite being such a small thing, and most women either hate it or love it.

From my own experience, when I grow my facial hair I get looks from groups of different women than when I'm clean shaven, and I've noticed when I grow it women that weren't interested, start giving signals.