20BiTeen is the year of "Ask her out ffs". You, yeah you, who have been crushing on this cute butch in your math class, or this fiery and flirty girl at the club, or the total 6'1" babe the you see every Saturday at Whole Foods with her dog, you can ask her out. I believe in you (and if she says yes then you will get an amazing success story to tell).

I don't know if she likes girls...

That's true. But if you don't ask her out, you won't have a definitive answer.

What if she says no because [whatever reason] ?

That's a worst case scenario. At least, you will be able to move on (I promise it will get easier with time). And as a bonus, you can congratulate yourself for putting yourself out there !

But I don't know how to talk to girls...

WRONG. You are one. You (most likely) are a respectful person and know how meeting someone works.
If you are attracted to one girl, fake it until you make it, it gets easier every time, I swear.
Remember that YOU have the upper hand. You have the power to decide whether nothing will happen (if you don't make a move, nothing will happen obviously) or not. So get up and try something, push out of your comfort zone, she won't judge you if you are a little bit awkward.
Words of wisdom on how to flirt with women here

But what if I'm too awkward...?

Deep breaths. Focus on the thing you want to happen (asking her out). She's a regular person just like you and I and chances are that if someone respecfully flirts with her, she won't take it badly (and PSA : no, you are not a creep for letting less than chaste thoughts cross your mind. Just don't be weird about them and only express them in the correct context.)

But what if...?

NO ! No "what ifs" ! You never know what can happen if you ask her out ! Some success stories :

Simple but effective
Well... It worked !
Eye contact, man
Another one !

Remember, life is too short to not ask the girl you like out !