I'm from Greece so you may find my text a bit wrong... but anyway...
Im 15 years old and I'm in love with a girl 15 years old too... we are at the same class but she is in another classroom.A year before I argued with a friend of mine and then he told her that I'm in love with her... She didn't believe him but this is not sure... Then,this year,when the season begun, I tried to talk to her... I have tried thousands of times... but the ''bad'' thing with me is that I don't have the courage... I am sooo skittish that I can't even talk to her best friend (her best friend knows that I like her and she keeps it a secret)... I don't mean I can't talk but I want to say that I'm soooo shy that I can't get even in to her class to speak to her friend... Im trying every single day to talk her at school and when the schoolday ends I only think that I can talk to her tomorrow... and then tomorrow... and then tomorrow... but I started doing that from September 2008 and now it's April 2009 and I haven't yet... and I'm sooo shy... I try to take the courage but I can't... what shall I do?the season ends in 2 weeks and I don't want to lose her forever... I want to mention that we are not friends,we don't speak together and I don't know if she likes me but I know that she knows that I like her... also she lives far away from my home so it's imposible to be out of the school... what should I do?. At the last moment that I have taken the decision to talk to her something happens in my head and I stop... please somebody asnwer me!what shall I think at this moment?

P:S... I want specifically want myself to talk to her... I don't want a friend of mine to do that for me...

You ask what you should do? You already have the answer. TALK TO HER.

He said he doesn't have the courage to talk to her I wish.

You could try doing some public speaking at your school, or join a debating team, anything to boost your confidence.

I agree with Shazamataz. Sometimes it's easier said than done, but once you do these things and build your courage, it's all worth it. You can practice also by calling to order a pizza or such. That actually used to help me when I needed to help with my shyness even though it's weird. You can even try sending her flowers or something from you and you won't have to talk to her but you'll still be saying you admire her and she may even come to you. These are just personal experiences and guesses. I wish you the best of luck!

He said he doesn't have the courage to talk to her I wish.

You could try doing some public speaking at your school, or join a debating team, anything to boost your confidence.

There's only 2 weeks left, there's no time to do some public speaking or join a debating team. You're talking about long term.

Find a good friend and get him or her to give you a push. Sometimes all you need an encouragement from a friend to get you out there.

Another option is if you have common friends, like the friend that you've been takling to? Maybe that friend can help you by setting up a chance for you to talk to her.