well you need to find a reason to call or text her after you get her number.
You can't fuck a #.
Someone mentioned on this site saying something like this
"oh whats the one song? it goes like nan nann nana, it's right on the tip of my tongue"
Later on you can send her a text saying "oh its blink 182 all the small things"
When i get a number I'll send her a text in about 5 minutes "whore

" She'll wonder who it could be and ask "who is this" even if you gave her your number at the same time.
I'll respond with "how many random people do you give your number to? its trackjunkie!"
her "lol

"
me "nows a good time to save that number so the next time I text you we don't have to go through this"
now she's expecting you to text her, wait a few days and you'll see she'll text you wanting to know what you're up to.
Orrr I recently tried this one with good results, met a girl, got her number, called her 20 minutes later, told her I was going out, asked if she wanted to join, and we didn't even leave the house.
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Blogs and summaries of everything I have learned and field tested.