I've been told that I'm telling instead of showing when I say my characters' eyes sparkle 'mischievously.' How do you describe something like that? I've been looking it up and trying different tricks that usually help, but nothing is working.
Eyes that sparkle with humor, mischief, or ja ne se qua are already ‘showing.’ The phrase is so well-worn that it is not recognized as a deeply internalized observation of one person’s attraction towards another.
What that writing advice is shows me, is that whomever is you telling this are trying to cloak their feedback inside an appeal to authority — their appeal to show don’t tell.
What they should have told you was that phrase is cliche. And, if it is an important moment in the story, then it deserves powerful narratives and description and not tired old retread phrases written by god knows who over a hundred years ago.
This doesn’t mean that we should never use cliches, they are true memes. Furthermore, because everyone knows what they mean, they are very efficient ways to communicate elements about character, setting or mood — It was dark and stormy night, he was a man that looked foul but seemed fair.
In my opinion, cliches work best went the stakes are low and there isn’t much at stake in the story.
Show it elsewhere:
There's nothing wrong, in my opinion, with having some tell in your show. It is, in fact, very difficult to eliminate all together. To carry off the show with less tell, you'd need to communicate the intent with other body parts.
So the person has a smirk on their smiling face, and their face crinkles a bit as they tell a sarcastic tale. Their eyes glint as they squint. They seem ready to break out in barely-suppressed laughter. A point-of-view character might recall this expression from another time when the character did something else full of mischief. The person might bounce with energy. They relay their plans through conversation. If it IS the point-of-view character, then you have their own thoughts you can reveal.