Writing dialogue, I am literally in the audience, watching my characters, typing down what they’re saying. Their voices are even unique. I can hear the cadence, their inflections—the whole nine yards. Daniel Day Lewis said he experiences the same thing when acting. When I heard that (since I think he’s an acting god), I almost swooned. If he wasn’t older and happily married, we could have had something.
Regarding tips, I would say listen. Don’t make something happen. Let it bubble up. That’s when the magic comes.