We had an editor from Harvest House attend the Central Oregon Writers Guild meeting last night. He gave a talk on dialogue. Though I do most of what he was talking about, I thought I'd put down a few of the things that resonated with me.
1) Would the dialog be interesting enough for an eavesdropper to wonder about what is being said?
2)Let dialogue show the emotions.
3) Characters should talk to each other and not the reader.
4) Use "beats"* to show actions, define character, or vary the rythm of the dialogue.
5) Resist the urge to explain the dialogue. If you've written it well, there is no need to explain it in narrative. RUE
* A beat is a bit of action mixed in with the dialogue that you use rather than tags like he said.
The thing I like best about belonging to a writing group is no matter what the topic the speaker discusses I always either pick up a new little kernal of knowledge or I reinforce what I already know and do.