Hey bro,
I'm assuming from your post you're talking about situations where they ask for your digits INSTEAD of giving you theirs/number exchanging.
I forget if this is from Style or Mystery or someone else...but it's in either The Game or The Rules and it really does work.
Take a pen and some paper/business card/napkin/whatever the fuck.
Tear it in half. Write your name and digits on one half. Then slide her the pen (this is not a euphemism

) and the other half of the paper. 9 times out of 10 she'll just write her details, and then you swap papers. If she doesn't, she looks like a douche. If she looks blank or questioning etc, playfully make her seem 'simple' for not understanding/complying.
Getting a number shouldn't be too hard if you've followed the steps before properly, judged her attraction/compliance etc.
It's the day 2s/avoiding flakes where the real trouble starts
