I have recently met a girl I like at school. Problem is, I don't know
how to ask her out and wheather or not I can ask her our or get her
phone number at the current stage.

Here's some background info I would like to share with you.
I am an Asian and she is Caucasian. That is, I don't know what the
western convention is and all the thoughts, both my own and my
friends', are based on asian culture.

We have been having short talks over the last couple of weeks. Most of
the times we talk about how we are doing in our courses. Occasionally
I asked her what does she do on weekends or what type of movie she
likes. From my point of view, I am the one who always start the
conversation, which to me is like that she isn't quite interested in
me.

She almost always stays with her friends from highschool, so it is
quite difficult for me to get in that little circle. As far as I can
tell, I don't see a chance to get into that circle. I could go to her
when she goes to study or work on her assignments but I am not sure if
that would feel like an invasion of her privacy because it would
probably feel like that I am folloing her wherever she goes.

I am not sure, at this stage, if asking her our is appropriate. Or,
perhaps, I should get her phone number or MSN first before ask her
out? My friends said that she would probably feel quite weird if I ask
her out or try to get her phone/MSN because we do not know each other
that well yet.

What do you suggest me to do? What is the western convention? Is
asking her out or getting her phone/MSN at the current stage
appropriate?