Make sure to join one of the gangs when you get there, don't drop the soap in the shower and it's pretty much shank or be shanked. Watch out for the guys with teardrop tattoos.
Ummm, that's prison, not high school. Sometimes it might seem like it is though.
Seriously though, lunchtime is a pretty good time to find and talk to people. Find a table and talk to others. Before long you will have plenty of friends. High school is a whole different world you are about to enter. Enjoy it while it lasts. I hate to sound like my parents, but these are the best years of your life, enjoy them, and join a school club, or sports. get involved in school activities.