For a writer there are many sources of inspiration. Going to coffee shops and just watching people. The news. Other books. Films. There is literally hundreds of different things, but most of all it is music. Tarantino can write an entire scene from one bit of music. The sound of the Oboe or the strings of a violin. The tones and rhythm of a piece of music can conjure images of anything for a love scene to a horror. So authors get listening to some tunes for that next scene.