Well... Have this girl who is not in my class, not on my social circle , we only cross eyes all time in the campus.But, have something in she that makes her intersting ( beyond her beauty), and i never try to aproach in girls who i dont know, or never speak with , or dont know anybody who is friends with . So, what i do in this case ,Only to approach?

It sound like you have AA.

Walk around your campus and when you pass someone just say Hi. Once you get comfortable striking up conversation with people it's going to turn into a natural reflex and your comfort will throw out a comfortable vibe.

In my current Campus I started with only about 1 person in my social circle. Soon after, when walking in-between classes, I'd pass by people and say "What's up, man" or "Hello" to everyone. Eventually, a girl who was nowhere near my social circle held a door for me and by reflex I said "Thanks, you're like my personal door holder" with a relaxed smile.
Turns out she was very cute, from there we had a nice conversation, departed, and I went off saying Hi to people.

Once you're comfortable with talking to people you're not familiar with just walk up to her before you can think and strike up a conversation, even if it's about the weather and get to know her.

Talk to her dude its college. Name? Major? Sorority?, wanna come to my dorm and smoke? Boom.