This title was a Facebook post from my publisher earlier today. The main point never JUST tell.
Showing happens in the narrative. It is in the descriptions, dialogue and action.
Show, do not just tell good advice, something of an adjunct to Laurel K Hamilton’s, and others, but this particular quote is attributed to her, “One of my rules is never explain. A writer is a lot like a magician, if you explain how the trick works a lot of the magic turns mundane.”
Knowledge imparted through the narrative allows the reader to build the writers world in their own mind, this is a writers true magic. When we tell the reader and/or explain too much, we deconstruct the world they have built from our words. We do not explain or tell the reader everything, how the raygun works for example, it is sufficient to say our character shot his raygun at a target. We do not have to explain the physics of the weapon or the color of the ray. The reader provides it.
When we begin explaining the weapon and the color of the beam etc, we may well be taking away from the reader’s enjoyment of the action. That said, there are times and stories, where there is a need to occasionally tell to advance the story. A short story may not have the words to allow information to be completely narrative, so we must tell a little to aid the reader in creating a world from our words. Advance the story without causing undue confusion. And one thing is certain to me, anytime, as a writer, when just telling is needed, it should be done to advance the narrative not replace it.
When My Worlds Collide 