One of the more common tenets of cinematography is that there is no "right way" to accomplish a look. However, in the pursuit of a high-quality image that will best convey a story visually, some standards exist that can assist in the creation of a professional image.
My question to everyone is: What are these standards for you, and why? In thinking about this question, permit me to ask the same question in the context of musical composition.
There is no correct way to compose a song, but many artists utilize musical scales as guidelines to aid them in creating quality music. What would you define as the equivalent for lighting, or the "musical scales" of cinematography?
In my endeavor to create quality images, I often find myself asking questions about what separates a professional image from a non-professional one, aside from the limitations imposed by equipment quality; great images can be captured with poor equipment, and great equipment can render poor images.
What standards do you apply for yourself when creating quality images?