If I can give you one piece of advice that will change your life completely it would be to sign up for a service project, and do it solo. There is just something about thrusting yourself into a totally new environment with complete strangers that helps you form the most amazing friendships.
A few summers ago I signed up for a 5 week volunteer/adventure trip to Costa Rica. To this day it has been the most amazing, life changing, happiest 5 weeks of my life. And if I could go back to being on that bus with 40 of my closet friends, I would.
Spending time with anyone in a totally foreign place forces you to rely on the people you are with. Who cares if you only met them yesterday, you got the craziest email from your friend from home and need to gossip about it with someone. Everyone is on the trip to have a great time and make new friends, so it will not be weird for you to sit right down next to someone on the bus and start talking about anything.
I am usually extremely loud and like to have fun, so within the first 5 minutes at the airport terminal I had my bus group; girls who are also loud, funny and trying to party on our days off. After a few days more people began to gravitate towards us and soon even the most shy in the group became comfortable with everyone.
If you have a friend with you from home, it is harder to branch out and make these lasting friendships. You feel like you have to always be with them, pay attention to them and tell your secrets only to them. While traveling with a friend is awesome, service trips are better done alone. This gets you out of your comfort zone and really helps you focus on the mission (and the people) at hand.
Rather then worry if your friend is having a good time or if they don't like some of the people you enjoy, you get to sit where you want, joke with who you want, and put all your energy into making lasting friendships with the amazing people you get to meet.
Service trips usually thrust you into living conditions you are not accustom too, which means you all are about to get very personal very fast. We had to sleep with bug nets, kill crazy crab looking spiders and even smash a scorpion with one of our shoes. But we also had to work though each others panic attacks, help each other if one of us got to drunk, cheer someone up if they were homesick, and talk about bodily functions weren't just unavoidable, they were also hilarious.
Being embarrassed and ashamed is a waste of time when everyone is going though the same culture shock as you are. Lean on your new friends as support. After the first week of living with them, you might even feel closer to them then your friends at home.
Which is good because leaving them will hurt...a lot. I don't even want to think about how we all had to say good bye to each other in the airport, but friendships made on service trips last a lifetime. If you can travel together you can do pretty much anything, and when you see them again after however long, things will go right back to how they were as if no time has past.
So do a service trip solo, and you will come back from it with so many strong friendships then you could ever have dream of.