I understand appearance is often cited as one way to characterize, but isn't this misleading? What a character looks like doesn't necessarily reveal the truth about him.

A character’s appearance has the potential to reveal a lot about his personality. The man dressed in a three piece suit with disheveled hair who is glancing at his pocket watch is a very different sort of gentleman than the one in jeans and a tailored sport coat, hair cropped close to his scalp, a cigarette dangling between his lips. The woman who alights from the train carrying a stylish boho bag and wearing three-inch heels has different immediate concerns than the woman with a diaper bag, stroller, and infant snuggled in a carrier.

In this brief description from Russell Banks’ novel The Reserve, the reader can gather some important information about the young woman, Vanessa Cole, and her parents’ friends who are gathered at the Cole’s Adirondack camp:

The other women and the men, though they would no doubt dress more or less formally for dinner tonight, wore what they thought were North-woods hunting and fishing apparel—wool slacks, checked flannel shirts, rubber-soled boots: rugged Abercrombie & Fitch camp wear. Vanessa herself had on a pale blue sleeveless cotton blouse and a white pleated skirt that pointed nicely to her long, tanned legs and narrow feet.

But you’re right—appearance is not necessarily the truth and this is where things can get really intriguing. Sometimes appearance can say quite a bit about the person making the observations. In Flannery O’Connor’s short story “A Good Man is Hard to Find,” a woman who lives with her son and his family is trying to convince her son they should take a trip to Tennessee instead of Florida. Her perception of her son’s wife is revealing of her thoughts about the woman:

Bailey didn’t look up from his reading so she wheeled around then and faced the children’s mother, a young woman in slacks, whose face was as broad and innocent as a cabbage and was tied around with a green head-kerchief that had two points on the top like a rabbit’s ears. She was sitting on the sofa, feeding the baby his apricots out of a jar.

Appearance might be downright misleading and this can dig at deeper and more complex truths. In House of Sand and Fog, a novel by Andre Dubus III, Colonel Behrani, once a wealthy man in Iran, is in the United States working for the Highway Department. There is a discrepancy between how he sees himself and how others see him. He pays to keep his Buick Regal in the underground parking facility of the Concourse Hotel and, at the end of the day, when he walks through the hotel in his dirty clothing, he is angered by the treatment he receives:

And for the thousandth time in this terrible country I wished to be wearing my uniform, the perfectly tailored uniform of an honorable colonel, a genob sarhang in the King’s Air Force . . . But of course my uniform then, in the lobby of the Concourse Hotel, was damp work clothes with blades of grass on my lower pants, dust on my back.

In Karl Iagnemma’s short story “The Phrenologist’s Dream” Jeremiah stops his horse drawn buggy on his way out of town for a woman he briefly met 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.

She seems worn, evidenced by her scar and her “lusterless” braids. Yet, her “high forehead and watery blue eyes” make her seem young. This creates an interesting tension. Jeremiah—and the reader, no doubt—are intrigued to see how this reconciles in her personality.

Appearance isn’t always straightforward and hones, but it is revealing. Characterize through what your character chooses to project and what he accidentally betrays about himself.