Guys: what makes you consider a girl a best friend?

there are these two guys, and both of them are my friends, and they are good friends with eachother, too. i've decided that i want them both to consider me a really good friend so we can be like a really close trio or something, but how do i make a guy consider me like a best friend?? i dont want to date them, and we already have the friendship part down. we talk on the phone, AIM, we live in the same neighborhood and visit eachother, ride the same bus, have the same lunch pd and eat together, and yet they still aren't as close as i'd like them to be. i am kind of quiet, and they are more outgoing and witty, so how do i establish a tighter bond???? they talk about football a lot and im lost... guys, if you have a girl best friend, how did she become your best friend and not a love interest? remember: i'm a kind of quiet person... i dont dance and sing and scream around them and just let loose... yet... thanks!!!! =]