The 3 basic guidelines for describing characters

A wandering character has appeared!
Quick, describe her for XP!

It's judgement day: That's right, time to describe a character who has just wandered onto your pages.

Three things to keep in mind when describing characters:

1. Good, Evil, or Neutral?

Tone, tone, tone! Your character's role in the story should guide your word choice in describing them. The first time you introduce them is the first chance you have to foreshadow their role in story. How you describe characters also helps set the tone of the story itself, so choose your words with care.

2. Point of view

Who's describing the character? Keep in mind teenage girl probably won't be talking about her own "languid drawl and hourglass figure"; a workaholic librarian probably doesn't even associate the phrases "killer curves" and "sultry lips" with herself, and a streetwise cop infiltrating a gang has other things to occupy his mind than his "rugged good looks." On the other hand, a narrator describing a love interest might mention all those very same things, in extensive detail.

3. Significance to the story

How long will they be in the story? How much page space you devote to describing them will determine how significant the reader thinks they will be. Readers focus on what you guide them to focus on--the more space you devote to a character description, the more important the character should be. On the other hand, for tertiary characters, this means putting more focus on the setting and people around them.

Consider: Margot's dark eyes shone from the tears rolling down her fair cheeks, her rosy lips trembling. Even mussed and dull from two days of neglect, her hair was a glorious mass that brushed the small of her back; her long fingers trembled around the rose's stem with gentle reverence as she laid it on casket. He noticed smudges of an elegant red lacquer still trimmed the edges of her long nails.

Compare: Margot's inky-dark eyes gleamed from the tears rolling down her pale cheeks, lips trembling and raw from two days of grief's ravages. Thick and wild, the net of waist-length hair around her shoulders snaked out strands to tangle on a thorn of the rose clutched in a blue-veined hand, smears of blood-red nail polish still messily edging the long nails that clicked against the casket as she set down the rose.

Compare: The widow's tears poured down her pale cheeks, her unkempt hair as black as her dress. The priest and the other mourners spoke in hushed tones in the narthex, giving her a moment to say her final farewell in peace. She didn't notice me, in my shadow under the pews; I took care to keep it that way, since I had no desire to kill her. The man hiding in the cask should be my only victim this night.

Compare: My hand trembled on the rose I held, its sweet scent overpowered by the cloying incense. A strand of my waist-length hair had snagged on one of its thorns, and I thought about ripping the damned black hank out of my skull and just burying it with him, with my heart. But no, that would probably break the rose. He deserved better than a broken rose. Maybe I should have worn makeup after all, so he wouldn't be haunted by a baggy-eyed, pale-faced ghost of a wife. Then again, he'd always thought me beautiful even hungover and hugging the porcelain king; and funny how that memory should bring the taste of salt into my mouth, stronger than ever. My long nails clicked on the cherry of his casket, the remains of Radical Ruby still smeared in my cuticles. The color usually made me happy. This was not a day for happy things.
Same character, same scene, but four very different stories.