One useful piece of advice I received from a professor (which I then turned around and offered my own students) was to focus on specificity. That is, when you want to paint a clear picture for your reader in as few words as possible, aim to be as specific as you can with regards to your choice of nouns and verbs. So instead of saying "she stood in a clearing of trees," say "she stood in a clearing of birches." "The witch lived in a small, old house with a sloped roof and windows that jutted out the top" >> "The witch lived in a withered Cape Cod," etc.
Precise words do a lot of your heavy lifting for you. Also, I'd say to follow Chuck Wendig's suggestion for description--stick to giving your reader details that they wouldn't be able to fill in on their own. Most people know what the inside of a bar looks like. Tell us the details that make it your bar in your world--the broken glass swept into the corner, the gleaming jukebox that only plays rockabilly music. Get the most bang for your description buck.
Not to be rude, but I recommend doing the exact opposite of what this post suggests. I do not know what birch trees look like, nor do I know what Cape Cod looks like, and if these are all the description you give me, then you've painted no picture in my head at all.
In contrast, plain and simple language helps populate the scenery in your reader's mind without making them stumble around big or esoteric words. "She arrived in a bucolic meadow" does not paint a unique atmosphere in your head if you don't know what bucolic means - and many readers won't. "She arrived in a big, green meadow" does the job just fine. Your reader will imagine the field *they* like most.
In summary, try not to force your reader to imagine the picture you see in your head. That's where you start over-describing. You want your reader to leap right across your sentences without getting tripped in awkward or ineffective prose. Let the reader imagine their own version of your world. If my book talks about "an old, moss-covered graveyard", the last thing I want to do is talk about whether that moss is brown or green. Let the reader decide. A few simple sentences is more than enough.
This is also true for descriptions of the physical appearance of people. People like Stephen King spend pages and pages describing how someone looks... at serious risk of ruining the reader's interest. If your character is "the most beautiful woman in the world", then don't describe her. Let the reader interpret that for themselves.