What is a first-time visit to the OBGYN like?

I'm 18, but started having sex when I was 16. I had always known that either when you turn eighteen or as soon as you become sexually active that you should begin seeing an Obgyn regularly to make sure everything is going well down there, and to discuss other avenues of BC, plus anything else that may come up in that realm.

But In HS, I didn't have insurance and I hadn't even been to the doctor for a normal checkup in years, nor did or was my mom gonna know that I was having sex. Plus there's some neglect in there, but that's irrelevant (I wasn't gonna ask he about it, point blank).

But now that I'm older and can explore these avenues for myself, I've been able to set up my own appointment and I'm just curious about I guess proper etiquette, and what they're going to be doing exactly. How should I dress? Should I take meds beforehand? etc.

I'm a total newbie, but going in somewhat prepared would really help curb my anxiety about the whole thing.