My school (university) also just started, end of the second week now. And since it is my first year, I am also a complete stranger to everyone. But I totally agree with Karen when she says that smiling helps. People will be more likely to talk to you, and if you smile all the time, you will have an easier time talking to others, just because you are happy. I did that for some days, just smile at EVERYTHING, and it worked out.
The times that I start thinking about what others may think of me, I have no confidence left to talk to anyone I don't know, so I just try to avoid that by smiling at the thoughts :).
Another good thing might be just to sit next to someone, and ask a few basic question, like whats your name, where you live, etc. Or talk about movies, what they think of it. People love to talk about themself, so ask the right questions and you will have a good conversation in no-time. That doesn't make in instant friend, but it is a good start. You don't make real friends in one week (unless you spent the entire week with them, day and night :) ).
Just be careful that you aren't blaming yourself for your shyness, it is easy to do so, but it will make it even harder.
All the best, and keep posting!
P.S: And of course, don't forget that you have already made a friend this week :)
Acceptance is the key
Existential depression and Insecurity
Try to keep smiling! :)