All the above BUT I would have to add posing and expressions to the mix.

I 've seen many renders that would be excellent but the character posing was poor or unpolished or even a canned pose without any changes.

Very few canned pose packages you can buy are great straight out of the box...they're mostly designed to get you close with final adjustments to suit your needs. Expressions are the same. 

IMO, a greatly posed character in a poor render is better then a poorly posed character in a technically good render.

The trick is to do it all right and rarely does it happen quickly. Tweak, render, tweak, render, tweak, render....

...and when you think you're finally done, leave it alone and look at it again the next day and see what you think. Odds are it'll not look quite as good as you remembered.

My 2cents worth. I'm STILL working on getting good with poser!

i7 6800 (6 core/12 thread), 24 GB RAM, 1 gtx 1080 ti (8GB Vram) + 1 Titan X (12GB Vram), PP11, Octane/Poser plugin, and a partridge in a pear tree.

Oh, and a wiener dog!