How do I approach her?`

Just start small talk. Pick out something that is going on or the weather, just open the door for conversation and see where it goes. Don't feel intimidated a lot of the times we won't be mean. I get that I am intimidating all the time so as a mature person I make the point to talk to guys I am attracted to or want to get to know better, but as a college age person I was more reluctant to start dialog. Just compose yourself, happen to be in her vicinity and just talk to her as if you already know her. Don't make jokes if your not certain they would be funny to her--peoples humor differs so much and if you don't know her well she might think your corny and I would stay away from that. She is human and bleeds red just like you---the worse that could happen is she has a man already or is not interested then you move on, but at least you made an attempt and you can walk away knowing you tried. I am not really feeling that line "hey, I heard you go her." She might see it as stalker like you have been researching her. I would just step to her and perhaps give her a compliment--then even if she wants to shoot you down she would be less inclined to do so. "You have really pretty eyes (lips, hair)." or "I love that shirt on you the color really makes your eyes stand out." then introduce yourself to her that should break the ice.

just go up and introduce yourself and make small talk. it might freak her out if you mention you already know what school she goes to so ask her where she goes during the conversation.

Don't find it stupid.its natural. I think its good for you to first off introduce yourself and tell her that you noticed that she goes to the same school as u.if you can't find anything to talk about break the ice by asking what classes she takes up there. Then when you get to know her a little better ask her would she like to hang out.

Perhaps you should go up to her and strike up some casual conversation. Then try lead the subject towards schooling and ask her which school she goes to. Then you have something in common and you can talk about your school and so on.

Nope. It would come off like you're prematurely seeking rapport, which conveys neediness and is a turnoff for women. Try this instead:

"Hi! I saw you from across the way and thought you were completely adorable. I knew if I didn't get to know you I'd be kicking myself the rest of the afternoon. I'm _____."

Just talk to her!
How does the one that pointed it out to you know?
Does he or she also go to the same school and know her from there?

Anyway,m I think that should come out later in the conversation, otherwise you might sound like a stalker if it comes out wrong.