Hey guys firstly I would like to say I'm not some pua guru and won't pretend to be.
I have been developing my skills for a while now and I have almost perfected this down to a tee despite this I still get alot of flakey day 2's but it's better than before when I didn't even get a reply.
Ideally you want to take her back to your place and **** her because then you can easily transition into a casual relationship however this isn't always the best move or even a move you can play at all.
So you go about your usual game, open, banter and it's time to close do you ask for the phone number? NO
Phone numbers don't work: In my experience going for the phone number is difficult and usually pointless. Even if she gives you the correct number you will need to do a hell of alot of DHV'ing and Memory Jogging from the night before to build enough comfort for a day 2. Then you will need to try stay in contact without being too needy of course this is easier said than done.
Facebook is your friend: Most girls have iPhones, Blackberrys and HTC's even if they don't all you need is the name and you can add her on Facebook. Iv'e never had a girl refuse to give me her Faceboook before I think this is because they can easily delete you if your a creep and it is alot less intimate adding someone as a "friend" rather than giving your phone number away. Whereas on Facebook she can see your an alpha and not a creep just be looking at your profile.
It's all about the profile: Just make sure you have social proof i.e friends commenting and girls liking your statuses, silly pictures where you are having fun and simply delete or untag anything that's a DLV. I have changed my job title, religious views and political views to something silly this creates mystery. Don't give away too much information about yourself, I found listing my **** job was hurting my game.
Tag her: If your in photos with her go ahead and do it, sometimes that's how I open her I just tag her and don't say anything. 10-15 mintues later she will usually message me.
The conversation continues: The best thing is you can pick up where you left off.. if the private conversation dries up, you can comment on her status to stay in contact. I normally start by talking in statuses now after adding you can wait a few days to show your busy and then start bantering her. Playful negs work very well on facebook don't post lots of x's and babe's and <3's that's beta as ****. Also don't be the guy who likes every status or comments on every picture.
Keep a few on the go: The beauty of private messaging is that you can have a few conversations on the go simultaneously without the other girls seeing. It isn't necessarily a bad thing if they do see other girls talking to you though because that's a DHV. But this means you can arrange multiple day 2's without being a sleaze. If you are on a day 2 you can turn off notifications from individuals if you so desire.
Take your time: Don't be too keen to meetup too soon, wait at least a week and continue to be awesome and upload funny interesting pictures of yourself having fun in between times to hold her interest whilst showing that your interested but at the same time your not "that interested" if that makes sense? lol
It really is that simple! and much easier than a phone call because you can see things like mutual friends or interests and you have plenty of time to come up with cocky replies to her messages. My favourite day 2 is to challenge her to a game of pool. Things like dinner and the cinema are way too forward usually and this causes alot of flakes.
If you have any other questions I will do my best to help you

Peace