I only look at the picture right side up. For my own purposes either it works or it doesn't, and its orientation doesn't matter much to me. Tell me, those who do look at it upside down, what does it do for the final print, once you turn the print back around again?
When I evaluate a print I always look at it in exactly the same location, under exactly the same light, in the same tray of water, so that there are no undue lighting effects compromising how I view the tonality of the print. Since I always print on the same paper, I know what dry-down does compared to the wet print, so it's a good way for me to consistently judge the prints.
In all, I look at how the print values support the content, the gesture, the frame, and the mood. It's such a fascinating process.
I usually spot my prints upside down... that works to stop you looking at the picture and concentrate on the job at hand.
That's the only time I do too and was going to write it before I read your post. I find more spots and do a better job when I find myself only concentrating on spotting and not the composition of the photograph. But turn it around and up close to analyze the results rather than keeping it upside down.
Originally Posted by Nige
I'll agree with the OP - at least to the extent that I find that looking at a print from every angle helps me notice extraneous elements that I might prefer to deal with in a reprint.
Things like bright areas that would be best if printed down, and large areas of shadow that unless they are intentional could tend to distract.
I look at my prints the right way up. After all, that's how they are displayed ;)
One class in college that greatly improved my photography and printing is a composition class. Most if not all visual arts have to use these rules of composition.