There might be a more common piece of advice thrown at writers than "show, don't tell", but I'm not sure what it would be. Still, I go to writing conferences all the time and have writers new and old be unable to tell what constitutes showing, and what is telling. Here's a quick primer (and something we all need to watch for, no matter how long we've been at this):
Which of these two sentences is better, more engaging to the reader:
Jane saw that the window was unlatched. She knew that if the wind caught it, the rusty hinge would creak.
or
The window hung askew, unlatched. A breeze plucked at it and the creak of the hinge floated across the room.
The first sentence is telling. The author tells the reader what things look like. The second is showing, where the author puts the reader in the room and lets the reader see and hear. One key thing to eliminate to sharpen writing is words like "knew" and "saw" and "heard", all of which put the character between the reader and the action. Sometimes you want to do that, because you need the reader to see the character, but most of the time you'll do better by letting the reader be the character.
Here's another example:
The books were stacked in columns. Big ones were slumped against the bookshelf, with no space for them to go.
versus
Stacks of books rose like stalagmites from the library floor. Larger ones, with no shelf space to house them, slumped against the bookshelf.
Neither of these are bad, in and of themselves, but which is more engaging? Which gives us the better sense of the room? The first one is descriptive, but both of those sentences have the helping verb "were" in them. That's a key to "tell-y" writing. Sometimes there isn't a good way to get rid of "was" and "were", but often you can rewrite the sentence, as I did here, and eliminate the helper. It sharpens the writing, even without the simile of the stalagmites rising (stalactites are the ones that hang down, FYI).
It may seem that these are tiny differences, and indeed they can be. But tiny differences are what separate good writing from the meh, and over time, those differences will determine what gets published and rewarded, and what doesn't, just as kryptonite, while not immediately fatal, gradually turns Superman into just "man".