A while ago, luna_manar challenged me to write a rant on what I thought was good descriptive prose. Well, here you go.

1) Adjectives are powerful, and don’t go out of style. Use them sparingly.

I can’t get into a sentence like this:

The slender young woman tossed her long, silky dark hair behind her delicately rounded head and raised her toned bronze arms towards the distant marble ceiling, her skin glowing like mother-of-pearl as she waved her fingers in time to the tune of distant winds, her breath exhaling in pulsing rhythmic song patterns, her eyes dark with stygian promise.

The fuck? That’s fifty-eight words right there, sixteen of which are adjectives, one of which is an adverb, and three of which are devoted to a simile. This is far too many.
It also doesn’t make much sense. Her arms are bronze, but her skin glows like mother-of-pearl? Well, which is it? She could be glowing with magic, but the author hasn’t said anything about that. The word “distant” is repeated twice. “Pulsing rhythmic song patterns” is one of the worst phrases I’ve ever heard; if it means what I think it does, it could be rephrased as “exhaling as if she were singing,” but I’m not sure it means what I think it does. “Stygian,” which means “gloomy or dark” and comes from the name of the river Styx, is just showing off. I have no idea why it matters that this woman has a “delicately rounded” head, or how the watching observer, assuming the passage is from that viewpoint, knows her hair is silky. (Viewpoint is often a problem in dense descriptive passages. See point 2). Also, is all this action really happening simultaneously?
I wrote that passage, so let me chop it down:

The young woman tossed her long dark hair back and raised her toned arms towards the distant marble ceiling. Her fingers waved in time to the winds that played their music in her head. When she finally began to sing, the white glow of the magic through her skin nearly blinded her.

There. It doesn’t get rid of every problem; nor does it convey everything that was in the original passage. But it gets rid of the stupid contradictory skin tone, the viewpoint problem—it must be from her viewpoint, since she’s the one thinking about the winds in her head and being blinded by the glow of the magic—the time sequencing problem, the repetition, and the purple prose. And it’s only fifty-two words long to the original sentence’s fifty-eight. Much better.
Always remember that the premise of description is to make your reader see—not dazzle her with how well you know language or confuse her so much that she only notices muddled words on a page.

2) Keep the descriptive passages in the same viewpoint as the rest of the scene.

Here’s another traffic accident. Note the parts I’ve marked:

She smiled up at him with her delicately curved lips, and thought how very handsome he was, with his cornsilk brown hair cascading to his shoulders, his slender toned body, his deep blue eyes full of haunting sorrow unknown to her, and his skin the color of a burnt apple.He had had a tragic past, full of daring escapes, fit to be sung with a coloratura on the theme of sacrifice, but she didn’t know it. He gazed back at her and the thought that filled his haunted head was, ‘How eldritch she looks.’ She reached out a hand and stroked his hair, thinking how much she would like to take him home.

What a mess. The author starts out in the woman’s viewpoint, but at once we have problems. “Delicately curved lips” is an awfully vain phrase for a third-person narrator to think, and she can’t see them anyway; this is a slew into omniscient. She specifically doesn’t know about his past, but there’s a sentence in the middle implying that it involves escape and the utterly hilarious phrase ‘fit to be sung with a coloratura on the theme of sacrifice.’ How is it there if she doesn’t know about it? Another slew into omniscient, or floating ‘Pick-a-fucking-POV-already’-ville. Then the man thinks something, but we snap back into the woman’s viewpoint for the last sentence. By now I am seasick and crying softly.
This happens pretty often in descriptive passages. Once again, the author becomes determined to dazzle the audience; she thinks up a phrase and throws it in there, regardless of whether it’s the kind of thing the character would really say or think, or even has the ability to say or think. (A subtler occurrence is when a character who normally is very laconic suddenly starts rhapsodizing on about the heroine’s beauty).
Remember this lesson when writing a fantasy novel, and remember it well: You have the whole book to dazzle your audience and tell them the story. You don’t need to pack everything into one passage.
That includes knowledge of your fantasy world, by the way.

3) Don’t dump descriptive passages at the very beginning. Dear god, don’t do it.

This is a common problem across genres, not just fantasy. The author has a character running down some stairs to escape the bad guys. Does she plunge us into the chase, or even take us back a few paragraphs earlier and give us a glimpse of the character’s terror, so that we’ll root for him to get away?
No! Of course not! That would ruin Project Explain The Fantasy World! So we start out like this instead:

The Kingdom of Aria had been founded centuries ago by a Queen who came from across the sea. None of her people remembered her name anymore, but referred to her only as the Founder. Her picture looked out from the top of every mantelpiece in the kingdom, and Arians would sometimes gaze at her fondly, the way that one might gaze at a beloved pet. She had green eyes—green as the fields of Aria, it was said; golden hair—golden as the wine that sustained the kingdom, it was said—and pale skin—pale as the foam of the Dragonsdawn Sea that swept the eastern coast of the kingdom with unceasing motion. There was never a moment that passed in the kingdom that was not under her watchful gaze, that was not bound to the rhythm of her memories, that was not a part of the long history she had started…

Imagine paragraph after paragraph after paragraph of this. I’ve seen it all too often in amateur fantasy stories on the Internet. Instead of starting where the story begins—with characters, with conflict, with an immediate important plot occurrence—the author takes us “back to the very beginning.”
Remember that it’s hard for anyone to care about a place without people in it to anchor the caring. You can write the most brilliant fantasy kingdom in the world, and if you don’t make your story interesting, the audience is going to yawn, put down the book, and say, “Next.”
Describe the kingdom’s history later in the story (but not in one infodumpy chapter, please, another of the great clichés of fantasy). You’ll have time, and by then your readers will be considerably more interested in hearing it.

4) Don’t let description actively take the place of the story.

You know exactly what I mean if you have read Robert Jordan. It is no exaggeration to say that he spends more time on describing the clothes, gestures, furnishings, and wilderness in his book than he does on advancing the plot. This is one reason why almost nothing happens in his books now; he’s caught up with introducing minor characters and describing them, instead of actually having things happen.
A fantasy novel can be about place as well as characters and plot—Tolkien showed this very well—but it’s not about description, any more than it’s about characterization or exposition. The tools of writing are what makes the story; characterization makes characters. To demand that the audience pause and admire your description of rocks and trees and clothes and china cabinets and ships and shoes and ceiling wax shows that you’re more concerned with displaying those skills that advancing the story. The moment that description becomes the focus, you have lost the story. Description serves the book, not the other way around.

5) In some scenes, verbs and nouns are more powerful descriptors than adjectives and adverbs.

I have read many fight scenes where the author will describe the character striking a blow, then admiring his enemy’s armor and the color his blade glows and the shine of his teeth, then parrying his enemy’s blow, then noting that the way the snow fans up around them reminds him of his last fight in the snow, then striking again…
I always think this is madly hysterical. The character is fighting, and yet he has time to notice things like this? Bitch, please. He’s fighting for his life, yet somehow the pretty, pretty patterns in the snow are more important? I tell you, only in the mind of a description-obsessed fantasy author.
Scenes which need a sense of speed also need to be streamlined. The fight for life, the daring escape, the moment between life and death when the character is teetering on the edge of a cliff…nouns and verbs are your friends here, not “like” and all the rich ultraviolet stratum of adjectives.
Instead of saying, “He slid down the banister like a tornado advancing on the coast,” try “He hurtled down the banister.” Instead of “She tried to lift her dear comrade’s dead body, and found it weighed her arms down like a boulder” try “She hefted her friend’s corpse, and sobbed at its weight.” Instead of, “She looked down into the distant mad chasm, swirling with water like monsters, sending up a choking smell of thick slimy seaweed,” try, “She nearly tipped into the abyss, which swarmed with water, and sent up a reek of seaweed.” Sometimes you’ll need the adjectives, but not nearly as often as people think. And the more weighty your language, the harder it is to read through, and the more your chance is of slowing the reader down, sometimes making the scene seem not as serious. After all, if the heroine has the time to admire the stained-glass patterns on the window in front of her, is she really that worried about her life?
Rant on vampires is next, I think.