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.
One of the things I see new writers do is to give detailed descriptions of each character as they are introduced. They describe them head to toe, including every physical feature (hair, eyes, mouth, nose, skin), and everything they’re wearing. I find this obnoxious.
I prefer to give one or two features at a time, and feed physical or clothing descriptions in as needed. In any case, I like to keep it to a minimum, only using it if it adds to the story, or character development.
I want the reader to see the character for themselves. If I tell you that the skinny guy with horn-rimmed glasses and a pocket protector came from the computer lab, do I need to add anything? You see this guy because you know someone like him. Does it matter whether he has black or brown hair, or blue eyes?
What could we remove from that description and still see this guy in your mind? How about, the guy with the pocket protector came from the computer lab? I think you see the same guy. Maybe your guy is fat with long hair and baggy shorts. Maybe he’s got a flat top and pants that are too short. Does it matter? Probably not. He’s your guy. In my mind when I was writing it I saw a different guy, perhaps. The pocket protector is his character tag, and I’ll refer to it several times in the story, but that’s it.
In Ironweed, by William Kennedy, we meet Francis Phelan on page one, but get no description at all until page three:
The brothers looked at Francis’s clothes, his ragged brown twill suit jacket, black baggy pants, and filthy fireman’s blue shirt, and felt a kinship with him that owed nothing to blood ties. His shoes were as worn as their brogans they both had been wearing on the last day of their lives. The brothers read also in Francis’s face the familiar scars of alcoholic desolation, which both had developed in their graves.
(The brothers are both dead and looking up from the grave.)
It is important to the story that we know that Francis is wearing filthy, raggedy clothes, and that he’s an alcoholic, so that’s all the information we are given.
In Rum Punch, by Elmore Leonard, we meet Ordell and Louis on page one, but again get no description until page three, when learn only that one is a light-skinned black guy, and the other is a dark-skinned white guy. That’s it until page five when “Ordell ran his hand carefully over his hair, feeling the hard set, ran it back to his pigtail braid . . .” Then we get a brief description of Louis through Ordell when Ordell says to Louis, “. . . that shirt you have on, you look like you pump more gas than iron. Ought to have ‘Lou” on the pocket there. Clean the windshield, check the oil . . . .” A few paragraphs later: Ordell in linen and gold, orange crew-neck sweater and white slacks, the gold shining on his neck, his wrist, and two of his fingers. Just enough for us to get an idea of the kind of person he was. (We have already learned that they were both in prison, and that Louis just got out.)
Otherwise, we have only the way they talk to see them in our mind’s eye, and that's enough.
One last example. In All the Pretty Horses, by Cormac McCarthy, the only description of the character I could find (although I haven’t read it all, yet) was on the first page: He took off his hat and came slowly forward. The floorboards creaked under his boots. In his black suit he stood in the dark glass where the lilies leaned so palely from their waisted cutglass vase. Do we need anything else? No. From the dialogue and the action, we can see this guy. To me, he’s tall, thin and gaunt. Does it matter whether he’s short and fat? Not one bit.
So, go light on the descriptions, we don't need them.