His eyebrows wagged.
Her eyes narrowed to slits.
His brows knitted together, face contorting with a sneer.
Her eyes widened.
He offered a lopsided grin.
Her chin jutted outward and her mouth twisted downward.
I won’t beat around the bush here; sentences like these make my skin crawl (especially the eyebrow wagging). Not because people exhibit these expressions in everyday life, but because they’re so glaring when I come across them in the books I read. Nothing makes me fall out of love with a book faster than watching its characters’ mouths quirk all over the place and their brows do all manner of gymnastics.
But why is that? Well, for two reasons.
Reason #1: When it comes to dialogue, I’ve always lived in the camp that you shouldn’t venture beyond using the tag ‘said’. None of that explaining, cautioning, retorting, blurting, or spitting. Such colorful verbiage is a form of telling, but just as importantly, they call attention to themselves when your dialogue tags should remain invisible. You can apply this rule to facial expressions too. When your character’s face is twisting, knitting, contorting, wagging, and what have you, people might exaggerate these verbs since the degree to which your character twists their face isn’t specified (characters often take on a cartoonish quality for me when I come across these verbs). Physical expressions, when it comes to conversation, are like fire. Handle with care.
Facial expressions still matter, and are even necessary, but they should be the garnish, meant to accentuate the importance behind the emotional reactions they’re meant to portray.
Reason #2: You’ll notice that in the examples I opened with, I ended the list with ‘He sighed.’ You can hardly call sighing colorful verbiage, since there isn’t a simpler way to express something people do everyday. But you still want to stay away from physical reactions that are cliches. It’s likely your readers have come across hundreds, maybe even thousands of characters over the years who have done all sorts of sighing, shrugging, wincing, and shaking of the head. Most writers know about story tropes, but prose are equally vulnerable to cliches. So don’t be lazy. Pull yourself up by your bootstraps, really dig into all the idiosyncrasies people exhibit when they interact with their fellow human beings, and find new and vivid ways for your characters to behave so that they jump off the page and feel like real, breathing people.
Now, the caveat to this advice. I will never advocate for absolute rules in writing. Sometimes, a shrug just fits. But if you can limit yourself to one shrug in your entire novel, you’ll probably be better off for it.