Writers are spies.
What do most spies do? They gather information. They observe.
We’re like that. I mean, not 007 or even Austin Powers. We don’t have a gun (most of us) or the cool gadgets. We don’t have arch villain enemies though if you’ve ever had a negative review you certainly could imagine the writer of that review sharing brunch with Dr. Evil. Nevertheless, much of being a good writer comes from paying attention to details.
Occasionally this may involve ease dropping. What can I say? It’s all in the line of duty. Mostly though paying attention involves, well, paying attention. How does someone speak? What gestures do they use? How do they communicate fear, tension, anger, happiness, and amusement? It’s all out there in the world and we go out into it and eventually we report back. Usually it takes some time for what we observe to compost in that great pile of experience and observation in our mind, but out it will come eventually as we sit in front of our computers remembering and imagining our stories.