The truism, 'Show, don't tell,' covers a lot of territory.
On a 'whole-story' level this means plotting that uses dialog and action and internals to tell the story
rather than narration.
Not -- Twelve battalions converged on the small town of Chesterton, determined to quench the fire of the rebellion.
But -- Tony looked out the window at dawn. Red-yellow pinpoint lights circled the horizon, strangely, horribly beautiful. Campfires. The enemy had arrived.
'Tell' tells the story.
'Show' puts us inside the story.
Plotting for 'show, not tell' on a whole-story level,
means general avoidance of scenery, exposition, description, backstory, explanation
and all the other ways the author speaks directly to the reader,
where action can be used instead.
On the level of a scene, 'show don't tell', means information is conveyed not in narration, but in action and dialog. Information comes to us through the filter of a character's perception.
Not -- Jeremy was a hopeless gawk. He'd been that way since High School. which is narrration and the writer speaking to the audience.
Jeremy untangled himself from the front door mat, Karen's dog, appropriately named 'Trip', the overturned aspidistra and his shoe laces.
What a klutz. "You haven't changed a bit," she said.
which is action, an internal, and dialog.
One easy way to make sure we 'show don't tell' is to stay deep in POV. That helps.
Now -- sometimes you find yourself with information to convey that can't be easily put into a character's thoughts or words or shown by a character's actions.
This is a good time to ask yourself if you really need this information.
However, there are also many many times the writer must convey complex information, economically.
And the simplest way to do it is to 'tell'.
Joshua lifted the cup to his lips. Coffee. The true bean of it, and fresh. Coffee came to Latruria by caravan over the hills of Ghangith. That path had been blocked for months by the mountain bandits. The only other source was the sea route. Smugglers. Jandru's smugglers.
He set the cup down without drinking. "How long have you been in Jandru's pay, Madame?"
So sometimes we 'tell, don't show."
This is all part of a huge plot to drive writers insane.