Ask her out, but make it sound normal. If that doesn't work, you'll have to stop being shy ;] Dunno how close you guys are, if asking her out to a restaurant is like normal btwn ya guys, but good luck!
12 years old. Man, when I was 12 all I worried about is Pokémon cards. Charazards picked up all the grills.
Just walk up to her on one lovely afternoon and say, "Hey girl. I'm a male, you're a female, let's do what nature intended." That's just a joke. But anyways, your situation is like that of a dating couple and the man deciding how to propose, but on a smaller scale. Pretty much just ask her out at a place and in a way that would remind her of all the good times you've have, and everything you guys have been through. Remind her that you guys have been friends for a long time, and that the next step can make things even more enjoyable. My biggest advice, just have fun with it. Girls are attracted to men who are fun, positive, and confident.
Oath. Women want some who's confident not someone like me who can get shy at times . I learned that the hard way.
If you were 12 back then at 1956, you would play with your friends out there. If you were 12 back at 2009, you would be playing some games with your friends and playing cards If you are 12 now, you are concerned about puberty and grills.