Many writers whose work I've read in the last thirty years made the old mirror mistake. I even made the mirror mistake myself and it was in my second book, not my first.
Don’t have your protagonist look into mirrors, the placid surface of a clear pond or the shiny fenders of a waxed Kia to see what they look like. It's a cliché, as bad as a stereotypical character, or a predictable plot. Your readers recognize the writer at work, which can take them out of the story.
In Kill Cue, I had a chapter from the viewpoint of Veronica's father. Therefore, I could do this:
"She looked so much like her mother, with brown hair, a perfect nose, round cheeks, and a strong, square jaw."
In my second book, Extreme Close-Up, I am ashamed to say I made the mirror mistake:
"Superimposed on the plate-glass window between Veronica and Max, like a ghostly double exposure, was her own square-jawed face, green eyes, full lips, what her David called 'a perfect nose,' surrounded by brown hair to her shoulders."
From then on, I learned to be subtler. Some writers think a good way to describe the protagonist is to make readers believe the character is thinking about their own appearance.
Naturally, you can't write, "As Veronica walked she thought about her dark brown hair and green eyes." That's much too heavy-handed. However, you can find an emotional connection of some sort and do this:
"Veronica had been taller than other girls ever since her junior year in high school. Green eyes and long dark hair wasn’t a sufficient trade-off for feeling like a freak."
This would not be a break in viewpoint because we have been listening to thoughts we believe she would have.
A precise, visual description of your protagonist is of-ten detrimental. After all, your readers are identifying with this person, and they don't want to be reminded of the differences between themselves and the character. The readers strongest image of your character does not come from what you say she looks like. It comes from her actions in the story.
Readers need just enough information to be able to form a picture of the character.
Notice I did not say take a picture. They will seldom know the character to that extent. They will imagine how she looks based on a few clues you provide them.
However, they do not need those clues at the beginning of the book. Don't fall into the trap of writing too much description all at once. Give readers only a few details. You can tell them more as you get deeper into the story.
In Revenge in Reno, I drop in a little piece of Veronica's physical description in the first chapter:
"She put her dark brown hair in a hasty ponytail with a rubber band from her desk, put his card in her jeans pocket and asked him, ‘Why do you think I need your help?’”
I divulge more about her appearance in Chapter Seven:
"As a concession to the man she was about to meet, Vee changed to a gray pencil skirt and a blue blouse instead of her usual jeans and T-shirt. She eased into black ballet flats so she wouldn’t be too much taller than him."
Let readers get to know the protagonist the same way we grow to know a friend: A little bit at a time.
----- (From NOVEL SECRETS available in paperback and Kindle form.) http://smarturl.it/novsec