Don't listen to anyone's advice around here. Most of these kids suffer the same problem. I, on the other hand, have grown out of the awkward stage.
Confidence is key. Don't just walk up to her and start talking to her if you're in high school. That comes across as creepy at that age.
What you need to do is initiate a conversation with her without it being obvious that you did so just to talk to her. It's difficult but as long as you ooze confidence, it'll work. There are lots of openers around but without knowing your current status with her, I can't give you anything specific.
If you're looking to go out with her, you don't want to talk to her as a comforting person. That will get you friendzoned. Rather, act interested in her but don't overplay it. Joke around and flirt a bit. And DO NOT tell her that she's beautiful until you're actually in a relationship with her.
The main rule is to ignore chivalry. From lots of personal experience (not anymore but back from when I was socially awkward), chivalry gains you a one-way ticket to friendzone. Do not be nice to her just to show that you are a nice guy. Girls don't look for that in guys and anyone who tells you otherwise is lying or has never been in a relationship. Girls think guys are nice when the guy has his attention on her, not because he does nice things.
Honestly, I need a lot more details to give you more tips. Both about yourself and her.