First, be true to yourself because we are able to notice when guys are being fake to try to impress us and its not exactly that attractive, especially in the beginning. Later on when there's a basic relationship foundation it might be cute but for the beginning, no.
Also remember your worth, maybe you've heard that girls like being chased but sometimes when it's done we might not care anymore to return any feelings and actions since you're already wrapped around our finger. So don't let a girl tell you twice she is not interested, it's more attractive and would let her think about whether she's actually into you or not therefore not wasting your time.
As to what to say, I'm not sure for most girls but I'm going to assume that most might not be into that "tough cool guy" who's "too cool for you" act, just be a gentle, nice, easy to approach person. You could start slow by saying "good morning" and/or smile to make an approach without making a vulnerable approach. I met a guy like this where he'll say good morning to me everyday and then was able to have time to get the confidence to ask for my socials.
Just be the best true you, know your worth so don't let yourself be a second choice, and be easy-going so others feel safe and comfortable. I hope that helped a bit <3