Well, for me personally, the first time I asked my girlfriend out, I just asked "[Insert her first and last names here], will you be my girlfriend?" And it worked perfectly well. Whatever you think she'll respond to best, use. You have to be the judge of that. There's plenty of variations on this. Another classic one is just asking "Will you go out with me?" As far as a situation, you could ask on a date, in some place where you two are alone, or when you've warmed her up by doing something sweet for her :D. Just be yourself, I tell everyone that. Let it sound natural, and not forced or rehearsed. That's the best advice I can give you. Good luck!

'Hey ______, do you want to go out sometime?'

play it cool let her do the asking

dont let her do the asking..
as the guy, most girls want you to take the initiative
you can start by asking her to watch a movie with you or something (she will get the point that it's a date). and by there, you go on 1 or 2 more dates.. and then you can just say it straightforward "i love spending time with you, will you be my girlfriend"

ofcourse, there are shorter ways.. my first gf.. i just said "will u go out with me".. i ddint see her for like the next 4 days because i was on a trip.. and when i came back we both just accepted the fact that we were "together"

depends on the girl i guess? but the first way is probably the more mature and common way.

It's as simple as "Do you wanna go out?"

the classic "will you go out with me?" usually works
the only one time that i've heard that was different was "well. is it kind of obvious that i really like you?" and i said "yeah." and then he said "do you want to be my girlfriend?"

take a deep breath, and don't let yourself chicken out.

My advice would be don't, just put it out there that you like her and then let it happen, its sexy.
Or just do it, that works too, I like to be creative sometimes though

if there's a food place nearby you could say something like 'you want to go have coffee sometime?' good reason to start drinking coffee. then it's not so formal that you're asking her out. you just meet for coffee and you have something to do while meeting. if it's weird either of you can hurry it up and leave pretty quick too.

Sort of say "Hey you wana go to the cinema/park/facility-near-you sometime?"
And if she asks who's all going just say "Dunno, thought the two of us could just go? :)"
Something like that works for me most of the time