I'm actually a very quiet person myself and attempted to keep to myself back in high school. I ended up having several friends anyway, probably because I'm really good at fitting into any group, and didn't really start to try breaking ice with anyone until college. That was hard for me... I was used to moving from place to place (it wouldn't be an exaggeration to say I've attended at least 20 schools growing up) and somewhere between the constant moving, I just gave up on making the first move.
It became routine, I'd just sit around alone for 2 or 3 weeks and wait for someone else to break the ice with me. Then from there, I'd try my best not to seem like a creep. It works and I've learned to adjust my personality slightly for any group I'm currently in (I never really pretend to be anyone else, I just tone up less common sides of me and tone down everything else). But towards the end of high school, I realized that this way of doing things wouldn't last me forever. You have to be able to speak if you want to get anywhere, humans are social creatures.
So when I went to college, for the short period of time I was there, I made it one of my goals to break the ice with several people. Sometimes it didn't work, people would straight up ignore me, but you know what? Fuck them. If they can't be polite enough to give you the time of day, you probably don't want their friendship anyway. For the few cases where breaking the ice failed for me, most of them were successes. And the best thing about breaking the ice is that you decide who you feel like talking to.
Ironically, I ended up talking to a lot of people who were like me, quiet types that just sit there and never speak to anyone. So I gradually got them to come out of their shells and made some very solid friends. I think this is something that everyone should learn how to do. Even if you're nervous, well shit you'd just be like everyone else, I get nervous too... Just pick someone out of the crowd that doesn't look too busy and open up the conversation with any relevant topic.
Just watch a person's mannerisms and try to match it up. If you're nervous and you stutter and flop all over yourself... Don't worry about it. Even if you mess it up, there's plenty of people out there. Just try your best to keep in mind that people are just people and most likely aren't out to get you. Those few that are... don't even waste your time thinking about them. They're not worth it.
And I'll end it with something I tell myself quite often, "If you don't respect yourself, how can you expect others to respect you?" Loosen up, Manny. You're a decent kid that's really kind. Anyone would be fortunate to have you as a friend.