Do the words flow? Is this the right word? Does this make my point clear? Is there enough mystery? Is the mystery so thick the reader is lost?
I have my own methods to keeping my writing strong, but my way doesn't work for everyone. The brilliant thing about reading is that there are so many differences in the way people write, you can be transported into a character's head and consider the world in a way you never would've before.
However, it never hurts to have tips about how other writers improve themselves. Even if the advice isn't spot on, it can generate ideas about new ways to look at things.

That being said, we'll move on to the meat of this post--visualization.
I recently finished reading Fangirl by Rainbow Rowell. I got completely sucked into her world. I kept trying to put it down, and I physically couldn't. Every time I was forced to walk away, I was still living in the fog of her words.
As I read, I asked myself questions, just as I do when I write. What can I draw from her example that will allow me to have the same hold on future readers?
A memory came to me while I was pouring over the pages. Two years ago, I was standing in line for lunch at the Pikes Peak Writer's Conference when I heard two people behind me discussing the last class they went to.
"Apparently," one of them said. "Metaphors light up a different part of your brain. They bring visual understanding in a way similes can't."
Since I didn't go to the class I don't know everything that was said, but that thought stuck with me. At the time I didn't know how to apply it to my writing, but after reading Fangirl I finally understood.
"Her skin sparkled like gold."
It's not a terrible simile. Pretty much everyone knows what gold looks like. On top of that, gold brings thoughts of luxury and refinement. But what if that simile was a metaphor instead?
"Her skin was gold. Just as soft as twice as radiant."
With one little change, it went from pretty good to beautiful.
I don't think it needs saying, but from now on I'm adding the word like to list of things to check during an edit. Who needs similes anyway?