It used to be that I would say something along the lines of "You're cute. Can I have your number?" But I realized that this was not the best way of going about things. Asking for the number means you are interested in scoring a number, not necessarily seeing the girl again.

Instead, I demand the number. Here are four examples of demanding the number:

"You're really cute. Let me get your phone number."

"You're absolutely adorable. Here, put your number in my phone."

"You're gorgeous. Here's what we are going to do: you are going to put your number in my phone and we are going to go on a date."

"You're very attractive. Would you like to hang out sometime?" (she says yes) "Great." (Hand her your phone for her to put her number in)

In all four of these examples, you are implying that the number is already a given. In these scenarios, it is a much smoother transition to getting the number. She also expects to see you again instead of assuming you are a player collecting numbers. Many girls give out their number for the attention, never expecting to see the guy again.

Most importantly, there is something more alpha in assuming you deserve a number from her instead of asking/begging for it.