I entered high school as a freshman two days ago.. I know nobody there aside from one friend. It really isn't as bad as you'd think. At here, at least, no real bullying goes on. If you try and talk to an upperclassman or something, and they ignore you, think nothing of it. They will usually be helpful though, as far as my experiences go. On Monday, after every class I'd have to ask " Where is class ___ ", and most of my feedback was good. For lunch, try and find a friend, or just walk up to someone who doesn't seem menacing and just be like " Can I sit here? ". It sounds stereotypical but it worked for me.
In most of my classes, everyone else talks to each other because they knew each other from Middle School. It isn't really that bad being a loner for the first few days. I don't really have any 'friends' as of yet. If you get assigned group work, its a great way to meet friends. Also, if you join band or a club after school and stuff, you can also get a lot of new friends.
Then again, you do have friends that will go to the same high school.. It probably won't be that hard to find them xD. If you have facebook just post your schedule and ask if anyone has your classes and stuff.
TL;DR: Don't be scared, its not as bad as you'd think.
