what i used to do to practice was (back when planet manhattan was full of people) i would just go there and inRP talk to them and just practice on the spot conversations.
I would make different things like for example a bottlenose with 2 pilots (brother/sister) or like an LPI snub is also really good for just talking to civilians and cops both. I'd go actually for the cop option for beginners because it is familiar to pretty much everyone.