Young guys don't have the skill set to approach and just start talking. The best I think you can do is co-locate with guys and hang in there till a friendship happen-stances. You may even have to take up a guy thing like basketball in order to co-locate. So, find a court, golf-coarse, bar where nice looking guys frequent. Then visit it at the appropriate time and shoot around till you get asked to play. I know when I was a kid I loved it when a girl played with us like one of the guys. Even if she stunk we handicapped her for heart and effort. If ya get swatted keep playing. If ya get knocked down just get up.
Just be careful with your heart. Realize that it takes a long time to really get to know someone. Young people tend to feel like they are in love before learning about the other person's deal breakers. Most of the time, those deal breakers are as simple as realizing the other person doesn't find you as attractive as you find them and therefore won't commit. That's when you find out what it feels like to be used. Like I said, be careful. Don't ruin your heart and become a mess like many many many other women out there. I wish I could say these things to my 15 year old but she won't listen to me.
Ok some of what skurge65 said was true like how guys fear rejection, you have to make sure that he is sure you won't reject him, or you could just make it easier on yourself and him by just going up to him and talking about anything random. It will be pretty obvious why you are going up to him but he won't care since you did it and he didn't have to (but this should be one of the only moves you should make he MUST do the rest). it is EXTREMELY important that you act confident. Notice I said "act" not "be". If your not confident (which is the usual excuse) pretend! Just like you are attracted to confident guys he is just as attracted to confident girls. And about what skurge65 said of a guys pattern and doing it as well... that's a big NO. He will get frightened and think you are obsessed.