My first time taking a dick was amazing. But it wasn't my first time putting things up my butt so that helped me a fair bit. I had made a dildo out of clay, essentially a copy of my own dick size-wise, and varnished it. That, along with some household items, was what went up into me first. And fingers of course.
The first actual real dick I had in me was at a college classmate's place, let's call him "G". It was on New Year's Eve, 1973>74 and G's mom was out babysitting the grandkids until the morning so we had the house to ourselves.
After a bit of booze, we retired to the bedroom and the games started. He was experienced and I was not, at least not with another person. G knew it was my first and he was willing to instruct a well as being conscious of taking it slow and easy.
We did everything in your basic vanilla gay sex repertoire. Sucking, fucking, jacking each other, lots of kissing and fondling. It was pretty damn sweet.
As for the fucking itself, he fucked me first. Fortunately, he was not big so taking him was not an issue. He was basically very average in both length and girth. There was lotion in use here - this was before lube would be easily available anywhere. But things went in rather smoothly. G fucked me for a while and, eventually, I fucked him too so I got to play both ends. We held off cumming until much later in the session.
I'd rate that, for my first time, as pretty much 100% success. G was aware, didn't rush anything, was careful not to go too far and too fast. He wasn't selfish, inconsiderate or other qualities that might make the first time a regrettable thing. Plus he wasn't huge so it all went really well.
Helped to set me up as the happy bottom / versa-bottom that I am today.