Some fine advice here from literary agent Nathan Bransford’s blog on making a novel work.
For example, on plot:
Plots are myriad, but plot structure is simple: hook, development (with backstory interwoven), climax.
It might be your hook that catches the reader’s attention, but it’s the characters who drag them in and hang onto them for life. Know thy characters. They must be real people, not two-dimensional cartoons, with real bodies, real mannerisms and tics, real foibles, dreams, insights, and idiodicies to be ashamed of. Know them backward and forward. Then don’t tell it all. Hemingway said, “The dignity of movement of an iceberg is due to only one ninth of it being above water.”
Exposition seeks not to just inform but to enlighten. Don’t waste your reader’s time with explanations. They’ve got brains. Let them use them. Leave out every explanation that can be inferred from the context. When you must cast light upon a scene, do it in context. Either you need to give the reader a breather between bouts of excitement or the tension can be heightened by knowing a little more about what’s going on. Take advantage of pacing to interweave backstory and exposition, but always keep up with your characters.