Show and Tell

We've all heard "Show, don't tell," but what does it mean in practice? Here's an example of telling (and of using the editor's bête noire, the manner adverb):

"I think we've gone off course or else I'm reading the chart wrong," Dahlia said nervously.

By you don't need to tell us that the character is nervous; you can show us.

Dahlia tapped a staccato beat against the chart table with a pair of brass dividers. "I think we've gone off course or else I'm reading the chart wrong," she said, gnawing at an already ragged thumbnail.

OK. Not great writing, but you get the idea. We're in the scene, observing the details, and we can draw our own conclusions.

Showing invites the reader into the story. Telling dumps information into the reader's brain. But of course you still need to tell some things. So what should you show and what should you tell? Writer/Editor Jason Black explains, 

You’re allowed to tell is anything that would be visible (audible, smellible, et cetera) to the reader if the reader were a fly on the wall in your scene, plus the viewpoint character’s inner monologue if you’re using that. All the stuff that’s directly manifest in the world of the story. Everything else, all the invisible stuff you want the reader to know, everything those flies on the wall would have to infer on the basis of what they observe, is what you need to show. Here’s the cool part: you show the invisible stuff by telling the visible stuff.

I'm a big teller in first drafts, and I always have to revise to show the story. How about you? Are you a teller or a shower?

—Kathy