How to ask for a guys number?

Just ask, be casual and friendly about it, a guy shouldn't turn you down.

---OR---

If you want to have fun and be smooth about it, maybe you could misplace your phone on purpose, have him call it so you find it and BANG! you got his number in your phone. Simple really . . . do what you want, just giving you another option to not be upfront and obvious about it, so you don't have to flat out ask him. Let me know what you think! lol =)

ask - 'do I have you number?' in a confused/thinking face. but don't make that your first line...
also,' can I have your number?' totally works fine too.

Just be cool. Don't worry about it. Just say like, "CanI have your number?" haha, can't go wrong with the basics.

get into a really interesting conversation that you "have to leave" in the middle of. And then say...well I'd like to finish this conversation sometime but I have to go...mind if I get your number?"

Just be casual and friendly. No guy would object to that.

Just say, "Well how about I give ya a call sometime?" and go from there.