Try to think like a Photographer.
See rendering like taking professional Photos. Any tutorials and books on how to make good Photographer apply also to rendering. this is not so much about technical things but about composition, framing, colour, contrast, balance and weight of shapes, static and dynamic lines, ...trying to tell a story with light.
From Robert Altman an famous film direction from last century, i remember the words: photography is "painting with light", which i took as title for may of my render courses i did in past, as i think this pretty much nails it down. All the rendering, including materials, is mainly about light, absence of light and composition of the forms.