But how do I show that to a cute girl I like?

I go to the same type of school I'm in the same spot with a guy. What helped me act the same around him and show my real self was the friends I have. Being able to go up to him and say I think you are a great guy and I would really like to get to know you. Saying that to anyone doesn't mean you are attracted but it shows them that you exist and want to become friend. And if people say that you are nerdy then prove them wrong and go after something you want before its to late!

Just be what you are,and start talking with her about something like"what is the weather like today" and after that start talking about some more interesting stuffs(the place where you are going out,the things that you or her are interested in and so on. )so at the end you can tell her that you need a coffee so if she wans to make you a company. But remember:be sweet as you are and only friendly at first with her. She will fall in love with you very soon believe me. So good luck

Honestly, if you really are sweet like you say you are, when the right girl comes along SHE WILL NOTICE IT. My advice? I would try shooting for girls that DON'T go to school with you. Go shopping at a cd store by yourself, casually ask/ or say oh you like blah blah blah band too? (don't do this if she's holding a b spears cd or backstreet boys cd)

Go to the grocery store by yourself, and give a smile to that cute girl scoping the magazine rack, it may seem awkward at first, but soon it will come naturally.
a smile shows "yes! I am okay to talk to. "

I think that you just need to spend time with her as friends and the way that you act and treat her will let her know what type of guy that you are. It is not like you can just say, "hey I am a sweet guy and I will treat you right. Lets date. " You really need to try and become friends with this girl first. Good Luck

Personally I would say don't listen to iamgonzo. He's wrong (save for the part up to "realize your goals" that part I will agree with though). But you don't need to worry about bullshitting them because I'm pretty sure that its not what your out to do.

Now then:
I like that your out to SHOW her that you like her. Most guys just want to tell her but showing is better. Most girls will analyze how guys behave around them and they will be able to tell if a guy likes them. If she's not too quick then your going to have to make it more obvious.
What I would say is treat her nicely and hang out with her. Its probably the one biggest thing you can do. Just ask her to hang out with you at the library, or anywhere else. Spend time with her. Also use body language, lean closer to her, look at her in her eyes. Little things.
But there is a little bit that you have to watch out for. You claim that girls treat you like the gay boyfriend which sounds to me like you fall into the "nice guy" category. If you treat her like you treat all your friends then you become another gay boyfriend. Take a stand and be a little more assertive. This doesn't mean become an asshole it means be a little more confident in what your doing. Treat her like you want her and don't become her willing servant. Sweet! = Lesser.

Go into the article section of this site and see some of the things people write. They will help you a lot. Just use your own judgment.

For the reply to iamgonzo:
". So be Strong in yourself and your goals to have this Hot girl laid out on your carpet naked. "
This should NEVER be a goal when your trying to attract a girl. Sex is an EXPRESSION OF LOVE WHEN ALL OTHER EXPRESSIONS HAVE BEEN EXHAUSTED. First you hang out, then you kiss, then you make out, then you date, and when you realize that you can't show her how much you love her in any of those methods that's when you have sex. It shouldn't be the goal the goal should be finding someone that you enjoy being with.

"So the TRICK is to LET THEM SEE IT FOR THEMSELVES, and off come the panties! "
NO. NO NO NO. I would downmod your post 100 times for this line. YOUR MAKING THE GIRL TRUST YOU SO YOU CAN BETRAY HER TRUST AND USE HER FOR SEX. Once this happens girls are DESTROYED. I've seen far too many cases where a guy betrays a girl and the girl always feels like she's the lowest thing on the planet. It destroys their moral and will make them hate men. If your going to use a girl for sex MAKE IT CLEAR FROM THE BEGINNING. What your telling him to do is the same as going to your best friend to talk about your problems but your best friend only listens to you because he wants to borrow your xbox for the next week. Its not a real relationship and its not something that you should do.

"Listening, This equals them trusting you"
Trust comes from them understanding you and understanding how you are as a person. It doesn't equate listening. This is just wrong.