There are many aspects of dialogue to manage, and different ways of tackling it. The aspect that interests me most is the subtext: not just what the characters are saying but what they mean.
Think of any family rows you might have. What are they really about? What on the surface is about what’s on TV might be about control. Argument about who you’re going to for Christmas dinner is really about relationships between in-laws. Someone reassuring a member of the family might be seeking to reassure themselves just as much – or even more.
When your characters are talking, think about what they’re actually saying, and then think about what they are revealing about themselves as a character. If the conversation isn’t working on both levels, then reconsider if it’s really pulling its weight.
Listen to conversations about you, or on TV programmes, and hear the subtext in them if you can. Here’s one quick example I overheard in the summer, by a stall that sold signs for gardens.
“Oh look, ‘Grandma’s herb garden’. Your mother would like that.”
“Yeah.” Pause. “But she’s not a Grandma.”
“No, but she’d like to be.”
Now didn’t that just tell you so much about the dynamics of that particular family?