At work, at home, on the bus, in the grocery store — folks are just being their authentic, unselfconscious selves. What a treasure-trove to mine for your characters and their dialog!
As writers, the best training you can get is to actively observe everything around you. While I’m not advocating eavesdropping, being aware of what people are saying, how they say it, and their body language will bring a ring of authenticity to your characters when you transfer the patterns of daily life to what they say and how they say it. Twenty or 30 minutes spent people watching at the mall, a sports event, church or just hanging out anywhere is valuable time that will allow you to enrich your characters and how they interact with each other.
To me, this makes sense for all genres of fiction, not just present-day-setting, literary fiction. Nobody wants to read stiff, wooden speech, or dialog that’s so clichéd the book should have come with an onion. Readers are smart, and they’ll know if a character doesn’t ring true.
People are people, as the old Depeche Mode song reminds us. They’re people whether they’re corporeal or fictional. While I don’t think we have to be psychology majors, it’s a great help to be an active student of human behavior and speech, filing away patterns and attitudes for use in our characters.
