When I read a draft of one of my books, I assess its worth as I go along. One of the things I ask myself about a scene is, "Does it sing?" What is the special element about this scene that will stay with a reader? What makes the scene? And if that element is missing, I have some work to do.
For example, imagine you've written a scene where a conversation is going on between two people in a quiet music room. You thought you wrote it well but as you read it again, an idea occurs to you.
You decide to include a metronome keeping time atop the piano. In the silences between the words of the couple, it is always there, monotonously ticking, as if asking them to keep pace. It lends a sense of tension and inevitability to the scene. Now it sings.
I think we have to ask this question with every scene. What's special about it that will make it memorable for readers? If this component is missing, it's time to re-imagine the scene and come up with a fresh angle, something that lifts it to a higher level.
In the end, it's a bit like touring your home right after you've decorated it. You look into each room and ask, "Does this room really work?" And maybe you realize the lighting in one of the rooms needs a little help. So you create illumination that showcases the best design elements of the room. And suddenly it sings. Quick, call Architectural Digest!
This has to occur in a unique way for every scene in the book. If that special something isn't there you may have a scene that works but is easily forgotten. Think about it in a design sense: what could you add to perfect it? What would give the scene added texture, fragrance, luminosity, allure? Until you answer this question I don't think you're done.
At least, this is how I do it in my books. What about you?