A girl knows you like her, but you aren't sure if she likes you. How to figure out and get closer to her

[edit] Steps

First you need to make sure that "she" likes you too. Ask a friend that "she" is not entirely "unknown" to her, to ask her if "she" likes you. Like, "Do you like ______________? I was just thinking that the way you look at him. And the way you smile at him. That you've been hitting on him."
Or ask a different friend to ask her what she likes about guys. Don't change yourself entirely, but show that side more often.
Ask her out. Girls usually won't ask guys out because she is shy, but some girls like to relate to the classic, 'Guys ask out Girls.'
Talk to her more often. Tell some jokes, make her feel happy in your company.
Get into the activities that she's in. If she's in chorus, then maybe you could join chorus, or be a stage hand. Just get into things that she sees you.
Flirt! During class, look at her and make sure she sees you too. Eye contact is vital!
Ask to borrow her notes. When note taking, ask her to see her notebook because you might have missed something. When you are finished, leave a note. Like, 'Nice handwriting.' or the best thing to do is compliment her on something you are too shy to tell her.
If you want her number ask her for it like if you are in her classes, then ask for it "in case you miss something."
Get her email, IM, anything to talk to her!

[edit] Tips

Don't lie about anything because then, your relationship is over before it even started!
Don't say something gross around girls, it just turns them off.

Some girls are really emotional and so be on the look out!
But if you hadn't noticed that's pretty typical, so please try to be understanding!
If she doesn't like you, give it time- maybe she will later.