If you notice a girl checks her fingernails by curling her fingers inward toward her palm, like a man would, you can bet she loves sex and will put out on the first date. She has also cheated on past boyfriends.
If she checks it with fingers outstretched, back of hand facing upward, she is going to be a drama queen with a heavy repertoire of shit tests. The more diva she looks when checking them in this fashion, the likelier she will make you wait more than a few dates for sex. A full ten seconds checking, turning her hand this way and that with nails glistening in the club lights, means she will flake on you.
A girl who doesn’t check her fingernails except for the most cursory glance, and despite your prompting, is a keeper.
You can get a girl to check her fingernails by mentioning something about her nail polish color, or the unusual way her fingernails grow and what that says about her. (Just make some shit up. For instance, “Oh, flat fingernails means you are very grounded.” Or, “Curved fingernails means you are hard to please.”) Watch for how she proceeds to look at her fingernails, and remember what this blog told you. Then sing silent hosannas to the knowledge dropped here.