Most Helpful Girl
I think before asking for their numbers, try to get to know them first and also make her feel comfortable around you. When you gain her trust, try asking in a nice way like: Hey, you're such a nice person. Is it ok if I maybe have your number so we could keep in contact?
But most importantly, be yourself and don't over flirt. Just take it slow and casual. Pay attention to what she's saying and don't joke too much.1