What is the least awkward way to get a girls number after you open her?

I'll be able to open in most situations, but the situation to ask for the number sometimes makes me feel like I'm nervous... Don't get me wrong, in most cases it works, here are what I use:

"Hey, you seem like a pretty cool person, but I've got to run or finish what I'm doing. Do you have an email? I mean, I'm not sure if you're going to stock me, so just to be on the safe side I'd rather get your email. (Then when the girl writes down the email, I usually say:) "Well, might as well put your phone number down. OH! and no flakes. You're not the flaky type right? I get a weird vibe from you that you are, but hey, I'll give it a chance."

" Hey, I've got to run, but here put your number in my phone and if I don't forget then maybe I'll give you a call sometime (with a smile on my face). [Then I'll say something about my phone being out of date]. Yeah, what do you have? Oh, a razor? You must be daddy's girl, what a total turn off!" Most daddy's girls I know are too modest, and social outcasts, but maybe you'll turn out different. Nice meeting you, I'll call you later."

These are just some examples I use, what do you guys use for the most part? I feel like when most my convos last less then 5min, then it makes me more nervous to get a number. Does anyone have a full proof plan they use?