As someone who was into the whole PUA thing for a long time, the battle is approaching in the first place. If you are attractive, 90% of the time you can get the number. But also, the confidence is incredibly attractive. I usually compliment on something that it looks like they took a lot of time on. For example, makeup or their hair.
"Wow. I don't usually do this but I really love that sweater you are wearing. It really brings out the color in your eyes"
"Hey. I am new in town and was wondering if you know of a good place to get a drink or eat"
"I don't usually do this but then say whatever in context of the situation (like a book store, grocery shopping)"
It's easier if you attractive. If not, it comes off as creepy.
I once was looking for dry shampoo for my hair and this girl came up and I sparked up a conversation on which one is the best. I made her laugh a little bit and before I knew it, had her number. That night, in bed. And we still hang out a lot.
80% of it is actually approaching and calming those nerves.