I have had a lot of bad approaches and very few successful ones. What I have learned it to first treat her like your meeting a new friend then politely talk to her a bit. Throw in a light flirt in there and then tell her that I will see her again, hope to see her again, or just ask for her name so I can add her on social media. Asking for her phone number seems to be something that is hard to get because their phone is so personal. Adding a woman on social media and then texting her that way seems easier. However sadly most of the time I get insulted or made fun of. So you have to take the very few good with the terrible. Ladies please just reject the guy. Don't insult him. I'll take a rejection any day over being insulted for approaching you.