I was thinking about what I said the other day--the reading plays part. It's a good idea and as a dialogue-sharpener it can't be beat. There are almost no wasted words in good plays/screenplays. And, like poems, they need to be read out loud to get the full effect. Maybe what I'm thinking about really only turns up in mediocre work: The little tag lines under a character's name that suggest line-readings to an actor.
That sort of thing. There was a joke at the studio where I worked--Riley Rueful. It came from a hint-line that read (wryly rueful) but for some reason it cracked everybody up and we turned it into a character we'd trot out when somebody was about to write something embarrassing. Probably, we were just tired. The point is this--if you see tag lines, don't pay any attention to them and don't use them in your prose.
For one thing, they're often adverbs, the world's laziest of all the parts of speech. Remember Tom Swifties?
"What happened to the lights?" asked Tom darkly.
I can think of a useful way to use them in first drafts, though: They remind you of some of the emotion behind the passage you're writing, and adverbs can be like little glow-in-the-dark highlights, places to go back to and work harder on.