How to ask her for her number? - 1

I really like this girl in one of my class and I would like to talk to her after school. We only have one class together and I would like to talk to her more. But, I don't know who to ask her for her number without saying really creepy. I have also never asked a girl for her phone number (I know I'm 16 quite sad. ).
Should I go like this:
Me: How are you?
Her: Good, you?
Me: Same.
Her: How was your weekend? (She usually asks me that)
Me: Great, I was with one of my friends on Friday after school. On Saturday I got my iPhone changes.
Me: Oh, I have asked you this yet, but can I have your number?

Or is there something better I can say at the end, do, or bring it up?

Also when do I text/call her? Should I do something unique and quite and text her right after she gives me her number like this:
Me: Hey, guess who!
Her: Jacob
Me: How did you know?!

Or is there something more unique and cutie I can do? Should I add a few more "y"s after "hey"?

What are her hobies? What are her favorite sports? What are her favorite movies? If I were you I would simply invite her to the movies or museum(whichever one she prefers), if she says yes, then ask her for her phone number to keep in touch & make the necessary plans. This way you don't creep her out and you don't look desperate.

Ask her

When you talk to a girl, you must not be thinking ''i'm in love with her' if you get what i mean. Girls like a guy who has a good sense of humour, but somehow they can figure it out what you are thinking just by observing your body language, so just remain calm while chatting.

Maybe like this:

Me: How are you?
Her: Good, you?
Me: (Seeing you makes me feel better haha) depending on how well you know this girl, or this (Never felt better!).
Her: How was your weekend? (She usually asks me that)
Me: Great, I was with one of my friends on Friday after school. On Saturday I got my iPhone changed but unfortunately my phone data was wiped out(just a little lie though) while updating or (something like that), so may i have the honour of having your number as the first contact in my phone? ( To show a little confidence is good.)

For the second part its not funny for her so you probably can try this: If she gives you her number, don't text her immediately, you will seem desperate to her. Don't use 'hey', instead start with 'Hi (name)' a little respect for a girl's name will do good for you. Text her about an hour after you got her number, its most likely the right amount of time, not too fast and not too long. You can start talking about common topics like school work. Start off small with school work first and then slowly talk about other non-school related stuff, good luck!