The first part of this post is a short exercise, and please follow the directions precisely if you want it to work.
First, read the following scene:
A man stood on the window ledge of a three story building. It was early in the morning, and there weren't any cars in the road below. He shuffled his feet closer to the edge. His hands fell away from the brick wall behind him so that he teetered unsteadily. He noticed a woman walking down the street in his direction. At first she did not notice him. Then, she stopped and looked up. She shouted, "Don't do it!" to which the man replied, "It's too late," before dropping.
Okay, now without trying to be consciously creative in any way, describe what you imagined the man and woman looking like in this scene. Don't reread it. Read the rest of the post when you're done.
I imagine the man to be about 5' 9", 35-years-old with brown wavy hair that hasn't been cut in the last few weeks. I see him in an affordable gray suit with a darker tie and a white shirt. He has a hairy chest. He's trim. He has brown scuffed shoes, a watch, no undershirt. He's Caucasian. His face is shaved. The backs of his hands are hairy.
The woman is thirty and 5' 5" and also Caucasian. She has shoulder length, straight mousy brown hair with lighter highlights. She wears a turquoise blouse with a dark printed skirt and sometimes when the wind catches it, her slip shows just a bit. She's slender. Her clavicles are visible below her smooth neck. She wears a thin gold chain and lght make-up. Her breasts are small. Her legs and toned. She wears high heels but not too high.
Who are these people? Well, for me, these are my concept of "average" people in my version of America. Whether or not they are really the average of every person in this country doesn't matter. What matters is that, when I start to read a book, these are the characters I imagine in my head until the writer has given me more clues. And, I'm willing to bet that these characters are at least sort of similar to the characters you imagined in your head. Maybe not the turquoise blouse.
When we set out to create characters for a reader, we always have to contend with the "average" character that most readers bring with them in their imagination. So, we cannot assume that they will know that the man is actually blind or that the woman has a blue beehive hairdo like Marge Simpson. More importantly, perhaps, we can't assume that the reader knows that a character is Guatemalan or Korean or Hawaiian without telling them. In the current status of American readership, if our characters have any trait that is different from the average person people imagine, the reader expects that trait to be revealed to us early on in the story. Otherwise, if they find something out later, they will feel deceived or that the writer has made a big mistake like a bad set up for the punchline of a joke. (Oh, what I forgot to tell you was that Ed was a two-headed horse.) I'm not saying that's right or wrong, but I do think that's an interesting idea to be aware of when we are trying to create unique characters.
The term "creative writing" implies that we are making something out of nothing. But, more often, I think we, as writers, are actually changing what is already there. A reader starts a story with preconceived notions of what to expect in their characters, and our goal is to alter that notion so that a character is unique and the reader can be entertained or engaged in some way.
(Of course, other things in the book can bias a reader's opinions. If the novel is called Eating Curry in Beijing by Yongqin Jiang, the reader might start off thinking that the characters could be Chinese. For me personally, this is sometimes interesting to learn since people often think that I am Latino or some other nationality based on my name.)
These assumptions by readers, including ourselves, affect what details we need to reveal and what we can take for granted, if anything. Sometimes, when describing someone we don't bother to get beyond a few superficial details. Sex, age, occupation, name -- maybe the length of their hair, their eye color, or the shape of their nose. But we have to realize that any detail we leave out will be filled in by the stats of this "average" person. If we really want to make a lasting impression and surprise a reader with a living, fully-formed and unique character, we need to keep the idea of what readers assume on their own and then create a character that deviates from their original image. What makes a person memorable is their originality, not their sameness. And, what if your character really is average? Even the most average-looking person has unique physical features if you look at them closely enough. Find that frog-shaped mole on the small of her back.