Smiling and maintaining regular eye contact are indications that a person is willing to engage further with you.

I'd frame it like this. If you're going about your day, when would YOU like a huge, hulking gay man to give you HIS number? Or an obese elderly woman? Because 99 times out of 100, that is when a woman would like you to give them your number. The level of interest a woman has in you is the level of interest you have in a giant gay man who finds you very very attractive and just KNOWS that if you give him a chance, it can work out great. Or an obese elderly woman who knows that she deserves love, and you're the one who she deserves it from, and she won't give up till she gets at least one date from you.