Thick mists hung heavily between the trees. A few beams from the moon struggled to pierce it. Odd shadows and shapes formed themselves here and there, inviting fear from any wayfarer who stumbled into these woods. Punctuating these shapes were the hootings of an owl, the howl of a lone wolf, and the sctritch and scratch of the small forest creatures.
The air was crisp with the smell of wildflowers and pine needles. Rays of sunshine filtered down through the trees, creating an ethereal effect. A deer is sighted for but a moment, and song birds sing sweetly in the trees. A squirrel scampers across the path carrying an acorn.
Would you believe me if I told you that I described the same forest both times? I did. Yet, the first time, the forest was scary, the second time, a place you would like to visit. What made the difference? It was my choice of words. I used words that conjured up fearful images the first time - who doesn't get scared when we talk about mists and shadows, wolves and owls? - and the second time I used cheerful words - crisp, wildflowers, sing, sunshine, ethereal.
True, the first time it was the forest at night, and the second during the day, but that was only because night lends itself to fear better.
Description helps set the mood of your book, therefore, it's important to know how do do it.
First of all, determine the mood of your book generally, and the scene specifically. If it's a cheerful scene, make your descriptions cheerful, if it's a scary scene, use scarier words. Second, use descriptive words. Now, that seems simple enough and straightforward, but it's a lot harder than you may think. It's easy just to say that the sky had storm clouds, but what about this: Angry clouds hung over us, threatening to loose their rain at any moment. Third, avoid being verbs. Use action verbs as much as possible. Action verbs? For description? Yes! Action verbs for description! You see, when you use the being verbs, the descriptions just sit there. When you use an action verb - then your descriptions pop into life - The yellow sun pops into life when you say that the smiling sun caressed us with his golden rays, doesn't it?
Of course, you're going to have to describe your characters as well as the setting. This is slightly trickier than describing setting, especially when you describe the main character. You see, you usually tell the story from the point of view of your main character - and how many people go about describing themselves! You can describe most of your other characters outright, but your main character, you have to be sly with. You can have them brush a curl of their brown hair out of their green eyes, or you could have them stand on tiptoe and wish they were taller. You can have them compare themselves to a family member that they think is more beautiful than they. Have another character mention what your character looks like.
However, do not over describe your character, or anything else. And don't describe any part of the scenery that is not absolutely necessarily to the plot or to the mood. If there isn't a secret message on the rug, you don't have to describe it to ever minute detail. That would just bore your readers and disappoint them when they realize that the rug has no significance to the story whatsoever. And, also, give your readers the benefit of the doubt - in other words, you can take for granted that a reader knows what an acorn looks like, or that they can remember what something looks like once you have described it.
Now, that's all I have to say on this subject. If you have any requests for me to write on, leave a comment with it, and I will try to write something on it.