I get that visualization and accuracy are some of the most important aspects in description, which, in turn, is one of the most important aspects of writing: BUT HOW DO I DO IT? Practice is the most obvious answer that immediately comes to mind, but what good is it if I'm practicing the wrong way? What is the right way? Same with reading, what good is it if I'm not grasping how to do it by reading? How do I know what to take from the reading I do for the purposes of getting a sense of the right way to do this? I'm so lost, and have been for years.. *smh*
I wouldn't say description is one of the most important aspects of writing. Yes, vivid, crisp description can be very powerful, but there are far more important elements. The ability to modulate tension is more important. So is creating and developing characters the reader cares about. But ther must be writers whose skill with description you envy. Study how they do it. Find descriptions that work particularly well, and dissect them thoroughly. Much of it will come down to a mastery of vocabulary. It need not ne a huge vocabulary, but every word must be spot on. Never use an adverb where an adjective will convey the same sense, and never use an adjective where the right verb will nail it. The right noun is important, but the precise verb reigns supreme. And never pound a descriptive point to death. You don't have to use "freezing", "icy". "frigid", and "arctic" to describe the wind conditions, choose the one that says it best.
When you're out and about, think of how you'd describe the situation you're in now, the cafe you're in, the forest around you, etc. Think of all the words that could fit for everything that you see, use words that you resonate with. And when you get round to writing your own work, you'll know how to make it all fit Also, use character reactions to show how the surroundings are like, as opposed to describing the scene to death.
I agree that description isn't all that important. You don't have to overdo it; in fact, if you do, you'll really bore the reader. Try this: Take your favorite novel and scan through it to find descriptive passages you really admire. Then, copy out those passages yourself, preferably in longhand in a notebook. That will force you to think about each word in the passages. Examine the passages in detail - what verbs, adjectives, and adverbs did the author use? What kind of imagery, metaphor, simile? If it's a great piece of description, you won't find cliches. The imagery will be fresh, unfamiliar, and therefore startlingly vivid. You will also likely find that the author did not really write as much description as you thought he did when you first read the book. He depended on you to use your own imagination to fill in the blanks, and, like any good reader, you did, without even being consciously aware that you did. As I've said before, the writer's most important tool is the reader's imagination. Forget about trying to force the reader to see the scene exactly as you see it. That will never happen. Instead, use just enough well-written description to trick your reader into imagining a vivid scene himself. One more thing: Use imagery that fits into your setting. If you're writing about a pistol duel fought between rivals in eighteenth-century France, don't say something like "Francois's shot missed, but Pierre fired with laser-like accuracy." There were no lasers in eighteenth-century France, so the image is inappropriate.