Is there anything that a woman can do to set off your "gaydar?"

Now of course I'm not generalizing lesbians, everyone is different in their own blah blah blah whatever, but there are subtle peculiarities that every social group has you know? I'm asking because in a world where most people are straight, trying to get girls will involve a lot of hitting on straight girls you thought were gay, and I'd like to avoid that situation like the plague. And I know the whole "go to the gay bar" advice but the fact is that my future girl is probably kicking it in a bookstore or a place with a lot of trees. I fucking hate bars too.

Anyway the tl;dr is that I need to be more adept at identifying gay girls so I don't offend the straight ones. And sorry for the throwaway account.

Also why is it "actual lesbians?" Is there an abundance of hypothetical lesbians?