I have heard from multiple people that eye contact is essential in letting a girl (or guy, I guess) know you’re interested.
But what is the 411 when it comes to said eye contact? Do you keep looking until she does? Do you then keep staring? Or is like looking at the sun? What’s the deal?
One element is to smile with your teeth. If a woman smiles with her mouth closed, it’s just a friendly thing. Old gf told me that and a couple of decades of observation have born that truth out.
Know that face you make when you really want to smile, but are obviously holding it in? That can work.
Making strong eye contact, holding-it-in-smile, then blushing away, just to look again with a full-teeth smile sends a strong signal.
OTOH, if you have to consciously think about how to compose your face, you better be a trained actor. Humans have a solid sixth-sense for the disingenuous.
In any case, don’t merely stare without expression. Yikes.
Very cultural dependent. I’ve been quickly recognized as an American because we tend to smile with our teeth exposed more often than other cultures.