Aspiring (and possibly even experienced) fictioneers should take a look at E. E. Knight’s list of twenty mistakes that are made frequently by story writers. Not only informative, but delivered with a bit of quality sass, too. My favourite is his re-statement of the "Chekhov’s Gun" rule:
"10 – Beaming in: I get confused when characters, gear, and important features suddenly appear mid-scene. It’s one thing for Sam Spade to reach into his bottom desk drawer and pull out a cached bottle of whiskey, you’re showing where the object came from. It’s quite another for you to suddenly mention that there was a German bayonet war trophy in plain view atop the filing cabinet in the middle of a fist fight."