I mention it in another comment, but the one of mine I'm referencing was a clever way a woman gave me her number. I can think of a few other ways I've witnessed it. My partner does burlesque and recently got asked for her signature for the first time. A wink or blushing could work as a compliment about your attractiveness. Somebody letting down their guard around you could be a way of telling you they feel safe around you. Even better if it's a cat. Going for seconds of your cooking. For me, there's a certain reaction when I throw somebody at the dojo that means: nice one! One of my friends gives rocks. Etc etc.