We've all gotten the whole "Who is this" response from texting a girl. So how can we keep it from happening altogether? I like to preemptively strike the whole texting chain right when I get the girl's phone number. To do this, I simply take her number and tell her..."I'm texting you right now, did you get it?" Then I text her simply "Jake" or something like "Jake is so hot" or "Jake, the hot guy from sky bar" etc. This allows me to verify her number, then when I text her next, she'll see my previous text with my name and have a chance to remember me and that i'm hot (small bit of NLP). This way I don't get a "who is this" text, and if she wants to ditch me she'll have to not respond at all, and then i've got my answer as to our future. If i'm taking a number and the girl tries to tell me that her phone's broken or some other bullshit excuse then it gives me a good idea that my effort with her wasn't as solid as it could've been. Knowing this information, I can try to get her attracted more and try again or I can simply fold my hand and go on to the next girl.
Now once you've gotten her number and texted immediately, you might text the girl at the end of the night if she's in-venue dependent and looks like she wants to hangout that night, or you can text her anytime in the next 1-3 days depending on your personal preference. Some guys like to strike when the iron's hot and text the next day and others would rather wait a couple days, even a few. I've found that both ways can be effective, and there's really no right or wrong answer here. Just make sure if you get a girl's number on a Friday or Saturday night that you're texting her before Wednesday of the following week at the very latest.