My high school music teacher used to tell us to think about the silence between the notes.
In life drawing my teacher suggested I look at the spaces between the shapes. What is the shape between the model’s arm and their body?
I think this is a wonderful way to come at dialogue. This way you can ask, what are my characters concealing?
Call me crazy, but I’m going to go away right now and write down what my characters are not saying to each other!