55% of human communication is nonverbal.
Which means more than half of what you say is nothing but expressions and gestures and eye contact.
Which means if you use nothing but “he said” and “she replied” to tag dialogue, your readers are missing half the message. Besides which, body language is also an effective way to show tone without “telling” tone. For instance:
“Hmmm,” she said unhappily/happily/thoughtfully. [All “telling”]
“Hmmm,” she frowned.
“Hmmm,” she smiled.
“Hmmm,” she tapped her lips with one finger.
We have the additional benefit of cutting the dialogue tag, “said,” which can get annoying in large doses.
Of course, use of body language isn’t limited to dialogue. You can say a lot without actually saying anything (useful if, like me, you are terrible at writing dialogue):
He hunched in his chair, elbows on knees, head in hands.
She bit the corner of her bottom lip, her gaze darting left and right.
He frowned, stroking his chin.
She leaned back and folded her arms, tapping her fingers against her skin.
He cocked one eyebrow, smirking.
There are countless other gestures to illustrate countless other emotions. Here are a few (in totally random order). Got any other good ones? Leave ‘em in the comments!
Run hand through hair
Tilt head to one side
Look in the eye
Gaze slide to floor
Nose in air
Look down nose
Push hair out of eyes