Here's a bit about Scriptwriting and dialogue, written by Michael Jacob on the Writersroom Blog:
'Good dialogue is economical, with not a word wasted, and while dialogue should obviously convey information, it should be information with attitude rather than information alone. People telling each other stuff is dull, and people telling each other stuff that they should already know is just bad. Attitude is crucial.'
I do get where he's coming from when he says 'attitude'. I love reading stuff, or listening to stuff that has a bit of attitude. I love writing with attitude, and it's something I'm going to keep in my mind, rather than is this just people telling mundane stuff to other people?
So, attitude is crucial!
I think getting into the character's heads is crucial too. I'm writing some dialogue for a script and I'm trying to be that character. Trying to separate each character, one from the other. That's quite hard, I find, but essential if there's going to be real chemistry or antagonism, or fear or truth, or all of those things.
This is also said in the Blog:
'The novelist Anthony Powell felt that one of the keys to avoiding the exposition trap was that questions should never be answered directly, which is a handy tip.'
So, with that I take it he means, never give away the full picture, but slip things in as the play/story progresses, to move the play along. Show a little but not too much. Leave much to the audience's imagination.
More on this later...