During the formative years, we avidly collect books on the writing craft and relish them like epic novels. Something like this: "Yep, that's for me. Amazing! That makes sense. Can't wait to try it." Then the day comes when our writing is no longer cringe-worthy. Congrats--you've just found your 'voice'. How much is a result of the writing aids? You probably absorbed gems of special interest, osmosis style, and now have an innate sense for what works and what doesn't. You might even donate your collection to a thrift store, to the delight of an aspiring writer. Let's look at the categories of reference, then a specific example from the many topics.
The Writer's Complete Fantasy Reference, by Writer's Digest Books, breaks it down thusly for us fantasy types: culture, magic, pagan society, commerce & law, races, myth, costume, arms, and castles. Your own preferred genre will benefit from technical books on travel, courts & police, government & military, as the shoe fits.
Just to pick one from a hat, The Scene Book, by Sandra Scofield, lays it out in four parts. First come the basics; event and meaning; and focal point. Part two covers pulse, tension, conflict, and senses. In part three we have characters, openings, and major scenes. The last section shows ways to handle narrative and become a critical reader.
Director vs People Person
Now we must choose a style, and that's a whole topic in itself. A quick study will show pros and cons of two major methods. THE WRITER DIRECTOR orchestrates a grand vision, unfolding it much like a film. Actors must follow the script, and it can be formulaic. THE PEOPLE PERSON creates vibrant, compelling cast we care about. But their strong wills can pull the story in different directions.
Getting In Character
Some writers use physical aids when getting into a character's mind. You might listen to that person's favorite music, sample their food, or admire the type of art they like. I'll use an example from my preferred fantasy genre: Gothic Fantasies, a book of paintings by Anne Sudworth. Depending on the scene requirement, these pictures help create the background mood you're looking for. Nuff said for now. Donate your collection yet? It's time to lose the training wheels.