First day of HS this week, what do?

My first day of High School is on the 12th, and I have no idea what to do.

I already have some clothes picked out and a general idea of what to do (just go to class and don’t make waves), but I’m wondering if I should do anything else, like find a club or friend group or something.

For context, I don’t really have many people I can call friends, and I’m mostly an introvert and very much prefer to keep to myself.