The best way to ask this girl out is?

[Cal]

There is this girl at school who I really like. There are almost 3 months that I like her and last week I could finally meet her. As she is in a different grade(2 years younger than me by the way) I can only talk to her on some specific days and for about 4 to 15 minutes. So, my question is: What is the best way to ask this special girl out so that I have better chances of her saying yes?
Should I at first ask her to hang out with me and one or two of my friends to let her know me better?
Should I ask her directly to go out with me?
(any other suggestions are indeed very welcome)

Some more details that I think could help to answer my question:
- As I met her last week we still don't know each other very well.
- I have some very good friends (3 girls) who are very trustworthy.
- We have one friend in common (a boy) though I am not a veery good friend of him.

PS: I don't usually go out with many girls so I would really appreciate if you could be a little bit specific.

[K. in Cleveland]

Well, I'd like to ask you what grades you are in... I know you said it is 2 years different, but the actual grades can be a big difference. If you're both in highschool, then I'd say probably the best way to do it would be just to say to her "Hey, I'm going to go bowling tomorrow night, was just wondering if you'd like to go too." Or whatever fun but casual activity you might be going to... just be direct but make it kind of fun and casual... I wish you luck

[Cal]

Well, I don't know what grade I would be in if I were American so I'll just tell you our ages, I am 17 and she is 15.
Just one more doubt, do you think cinema sounds fun and casual? I think it depends on the movie, but, what do you think?
Thank you very much K.

[Dan And Jennifer]

Hi Cal,

Nope, going to the movies / cinema is much more personal and intimate, since you're sitting together in a small space the whole time. It's really more of "a date" type date.

You want something more public and non-threatening, with other people around, so she can feel comfortable... like K.'s bowling suggestion for example, or other things along those lines where you get to know each other better and spend time together without forced intimacy and close quarters.

Good luck! Let us know how it goes.

[Cal]

Yeah, I agree with you.
okay, I'll keep you updated,
thank you!