My thinking, if a photographer wants to make the best pictures possible, there is only one step.
-Get it right in the camera.
(Sure there are some whom live and die by Photoshop and multi layered 17 image composite, but that is not most of us)
Of course there are issues to consider to make that happen.
1. Exposure. knowing that the camera's light meter is not always accurate one must think ahead of the meter and know how to get the best exposure.
2. Composition. Although they are called the 'Rules of Composition' they are more like guidelines. Asymmetry is better for creating interest.