Along with "Show, don't tell," comes the all time great writer advice hit: "Write what you know." Too often, this is taken as a restriction to mean you can only write about what you know. But the reverse should also be true: "Research what you want to write about." A writer should not live in a bubble, writing about whatever passes by. A writer should explore.
Since stories are about people, writers should explore people and all the many places they are encountered. I like to do something I call field work. Field work for a writer means going out to environments I'm not all that familiar with and observing human reactions and interactions. Which of these places are you familiar with? A church, grocery store, a traffic court room, the field at a little league game, a mall, a homeless shelter, a coffee shop, a hospital waiting room, a popular park playground, a political rally... think of all the public places you could go to observe human behavior. Now bring your notepad with you, and try and observe the goals of each person there. Does everyone have the same goal? Who are the people that participate the most? Who holds back? Can you observe a difference?
As a writer, you need to start training yourself to pick up details about people. If you're not used to doing this, your first attempt at field work might not produce much. But as you get better at it, you'll observe quite a lot. These details you pick up will really make your writing come alive.
Hopefully, you either went after a college degree or are considering one. Many writers naturally gravitated towards an English degree. If that's your choice, I would strongly recommend at least taking some classes in Psychology and / or social behavior of some kind. As a Sci Fi / Fantasy writer, I chose to get my BA in Anthropology because I wanted to be able to create fiction cultures from the ground up without having to base them on a pre-existing Earth culture.
Speaking of SFF cultures, how about next week I talk about how to create a fantasy culture from the ground up.