One thing that easily gets overlooked in writing is the sensory component. After the storyline is solid, the characters have unique personalities, and all the settings are imaginable for the reader, it is time to go though and make sure that there is sensory input.
We need to feed, not overfeed, the five senses of the reader. Consider it surround sound, but for all the senses. For example, when I write about the beach in Kathryn's Beach, occasionally there is mention of the hard packed wet sand. The dry sand sifts through her fingers, but it isn't just sand, there are shell bits (and assumed other stuff).
This is not the place to wax literary and go over the top with adjectives and adverbs in every sentence. Remember that less is more. Remember that the reader is an intelligent person with stores of experiences to tap. Avoid switching into the telling mode. Hint at things with simple additions, rather than lengthy descriptions. Allow the reader to tap their knowledge from a key descriptive word.
Keep the momentum of the story moving forward, rather than diverting to sidelines to describe things in detail. Not always, of course, but once in a while note a significant change in smell when changing venue. If something is different from what one would expect, for example a quiet bar, then briefly mention it. Or a fishing boat mysteriously floating unattended for days - wouldn't there be the smell of rotting fish from the morning catch on some fateful day? Basically, you don't want to have something obvious missing from the scene.
Visualize your story and once in a while add a small prop to the set. Read your ms aloud to a friend and both of you look for places where sensor items are missing. Avoid overloading the senses and it getting in the way of the storytelling.
Let me know if you try this and how it worked for you.