Being able to create human interactions that can seem authentic and interesting can come from various sources.
- Reading or watching TV and movies.
As you’ve said, it’s probably one of the best ways without physically being there, but it can also be different because they’re staged and scripted. So, it’s not entirely authentic. But it does give an idea on how people can talk, accents, interactions.
- YouTube.
When in doubt, YouTube it. Watching vlogs of people in groups or with friends can be really good because quite a lot of vloggers don’t script certain interactions. If you want to write about two guys who are best friends but you’re wondering how they talk to each other, how they interact, Sam and Colby is a perfect example of two dudes who do silly things. YouTube just brings you closer to that experience.
- Family and friends.
I don’t have any friends, but I do sometimes go to social events that my sister is invited to, like sometimes we’ll hold a painting night and some of her friends come over and hang out. Sometimes, she’ll be invited to a birthday party or wedding, and I’ll be invited too. Sometimes, I go to her church (usually for holidays - I rarely go any other day as I’m not religious), etc. But through it all, I am able to slow things down and pay attention to how people talk to each other, their mannerisms, what they talk about, etc. You don’t really have to sit somewhere and stare at people for hours on end. You just have to be in a place where people are - whether you know them or not - and consider how they talk and act.
- Past or current experiences (like work/school related).
And lastly, experiences you can take from memory or ones that have happened recently. As part of the friends and family version, another way is through work and school. Co-workers, customers, fellow students, teachers, and everyone beyond that. Even if you aren’t in school or aren’t working currently, you can always think back to past experiences and consider using it as a learning curve. Since I primarily write YA, for example, I think back to my past experiences in school (how students acted, how they talked, their conversations) as well as current-day students. I work with a lot of teens, and I have a teenage sister who has quite a few friends I’ve met and or seen her talk to. And even past the interactions, I can still use their actions/lifestyle/situations as a guide to help with storytelling (well, if I wrote contemporary teen fiction haha) because there’s a lot of tea that goes around. The teens at my sister’s school are hoes, bitchy, players, and crazy. Honestly, not too far off from my own experiences haha.
Overall, I like to think of it as psycho-analyzing and acting as if you’re a psychologist when it comes to people interacting with one another. Seeing how people talk and act can be the cherry on the top, but at the end of the day, it comes down to your environment, personality, opinion, and pretty much anything else that shapes who you are. If you utilize movies, shows, books, YouTube and other personal experiences while keeping in mind of the psychology aspect of it all, you may have good enough material to create well rounded characters who have authentic interactions.