IOI's:
*When you talk to these girls, are you waiting for them to ask you your name, or are you just giving it to them? If they ask, they're interested.
*How long are you talking to these girls before you go in for the number? More importantly, are you asking for it or are they OFFERING it to you w/o you having to ask? If you're doing and saying the right things they'll usually just give it to you.
*Are they asking you about yourself? When you open them up you have to ask about them, but are they trying to keep the convo going with you, or does it seem like you're doing all the work? If they like you, they should be asking all sorts of questions.
*When you ask for the number (if they haven't given it to you), are they hesitant, or scrambling right away for a pen? The quickness with which they're willing to give you the number will help you better determine if (a) they like you, (b) will give you a REAL number, and (c) won't flake if you call them.
You're thinking about it too much, but it's really, REALLY not that hard to get a girl's number - so long as the situation isn't forced. Real talk: I was at a show taping yesterday, standing in line with a hot chick waiting to get in. I did a side-comment (i.e. a comment that's not necessarily directed towards her, but said out loud in case she has interest and want to jump in).
I think I said something like, "man, they didn't tell me about the whole 'don't bring cell phones' thing." Yes, THIS was my opener - and she responded "yeah, they didn't tell me about it either." Next thing I know we're in a conversation where:
*She asked me about myself
*She asked MY name first
*She got into a story about how her short hair is sometimes long, then pulled out a business card with her face on it - as well as her phone number, facebook name and email address - to show me and keep (i.e. GAVE ME THE NUMBER W/O ME ASKING)
And all of this was within the span of 10 minutes!
Again, it can't feel like a forced convo - women sniff these out all day, and if you're awkward then the situation is awkward, and she won't want to give you ANY info, let alone go on a date with you.