What to do about boys?

Hi girls, i absolutely need some girl talk and help when it comes to getting a mans in my life. I’ve never had a bf and i think it was just because i wasnt in the right mind and i wasnt ready, i was also really self conscious before. But i never know what to do when someone attractive approaches me and talks to me and i often feel shy and end up seeming like a cold bitch to them i also don’t know how to flirt and how to get with guys i’m into because i’m scared of rejection. And i never know if guys are into me and what are ways to find out if they are? My mom always told me a guy will approach u if he likes u so does that mean if someone messages me online or talks to me irl they might be into me? Or does eye contacts and maybe smiles show that this boy is into you?