Scenes

Bronwyn Jameson states, “Every scene should advance the story, moving the plot and the characters toward the story's resolution and conclusion. If the scene doesn’t fulfil that purpose, then it doesn’t belong in the story.”

This is a very easy thing to forget when you’ve just written something hilarious or nerve-wracking or thought-provoking or otherwise brilliant, and you want to keep it in your novel just because it’s a good scene.

Good scenes aren’t good enough.

Every scene should contain action, AKA conflict AKA proactive characters.
Every scene should derive logically from the preceding action.
Every scene should directly cause change, thus provoking the following scene(s).

(This, of course, assumes you are writing a chronological piece, and not something like Pulp Fiction or Momento.)