It sounds obvious -- specific details are better than vague details -- but it can be easier said than done.
Look at the column on the left, then compare it to the column on the right. There's nothing wrong with what's on the left, it's just that what's on the right gives a much stronger idea of what is happening.
If you want a great example of how to do this, go read Laini Taylor's DAUGHTER OF SMOKE AND BONE. I visited Prague last summer, and let me tell you, Taylor's fanciful language describing the city at night is picture-perfect. Believe me, if you just said "European city at night," it wouldn't come close to telling you about Karou's world.
Do you need a perfect verbal SAT to write a great description? Definitely not. The most "unique" or complicated word in the McCarthy passage above is either "disclet" or "lozenge." The question is not big words -- it's the right words.
This is what I like to call the Project Runway rule. It's always best to start with way, way, way too much and then unleash your Inner Tim Gunn. If you don't start with enough, you may struggle to complete your look without starting over.
Part 3 forthcoming ...