How do I approach this girl in the hallway? (I'm pretty sure she likes me back)?

Ok, so there's this really pretty girl I see in the hallways throughout the day, and she's been showing signs that she likes me too. I've never been this sure that a girl likes me back, it's just a gut feeling. I want to approach her, but I'm really nervous. I've never really even approached a girl before, so I know it's gonna be difficult. I have no problem talking to girls, it's just when I approach them, it's kind of nerve wracking. I don't really think I'm bad looking http://oi53.tinypic.com/30rybfc.jpg and I'm not really afraid of rejection because I'm pretty sure she likes me too, it's just that I've never done this before, so I'm nervous. What are some tips on approaching her? Getting her number has been on my bucket list for like 6 months now, hehe.