You’re right; details of appearance can certainly offer insight into that character’s personality. I’m thinking about Sarah Bennet in Karl Iagnemma’s short story “The Phrenologist’s Dream.” The main character, Jeremiah is a phrenologist who examines the size and shape of the skull to draw conclusions about character. On his way out of a town where he gave readings, he comes upon Sarah, a woman he examined the day before:

Her arms were folded brazenly across her chest, but her high forehead and watery blue eyes made her seem sweet and young, like a child dressed in a woman's clothes. Her brow was marked by a frayed white scar. Her hair hung in lusterless brown braids, flecked with sand and bits of thistle, as though they'd been dragged through weeds.

Sarah is confident with her folded arms, but her inexperience shows thorough. She’s also unkempt and not consumed by her appearance. This is revealing information.

Iagnemma doesn’t linger long on her appearance. Just a few details do the work. Notice what Iagnemma leaves out. We don’t see Sarah’s shoes or the color of her clothing or the length of her sleeves. We don’t see the expression on her face or the length of her nails. We don’t see her lips or the color of her eyes or the shape of her legs. The details are not exhaustive. The focus is on the youthfulness of her face, as well as the state of her hair. These details define Sarah’s appearance, leaving room for the reader to imagine the rest.

In the short story “Cathedral,” Raymond Carver uses physical description to reveal something about the character being described and the person who is looking at him. Here, the narrator meets his wife’s friend, a blind man, for the first time:

The blind man, feature this, he was wearing a full beard! A beard on a blind man! Too much, I say.

Immediately, the reader begins to form a visual image of the blind man with the specific detail of the beard. At the same time, the narrator’s surprise reveals something about him. The story goes on to describe the blind man with a few more details. Notably, he focuses on the man’s appearance as it relates to his blindness:

But he didn’t use a cane and he didn’t wear dark glasses. I always thought dark glasses were a must for the blind. Fact was, I wished he had a pair. At first glance, his eyes looked like anyone else’s eyes. But if you looked close, there was something different about them. Too much white in the iris, for one thing, and the pupils seemed to move around in the sockets without his knowing it or being able to stop it. Creepy.

The narrator’s preconceptions about blindness and his interest in the man’s eyes are revealing. Both Carver’s “Cathedral” and Iagnemma’s “The Phrenologist’s Dream” use defining detail to accomplish physical appearance precisely and quickly. As Elmore Leonard suggests, there’s no need to linger.

This can be done with even more brevity, as Leonard goes on to explain:

In Ernest Hemingway's “Hills Like White Elephants” what do the “American and the girl with him” look like? “She had taken off her hat and put it on the table.” That's the only reference to a physical description in the story, and yet we see the couple and know them by their tones of voice, with not one adverb in sight.

Not all stories need to practice this much restraint. Still, Leonard’s point is important. You don’t need a lot of description to help the reader “see” a character.