Photoshop books and forum posts tend to focus on resolution, compression and using color spaces which capture the broadest range of colors.
But buyers of prints give dramatically different reasons for returning them.
The lesson of millions and millions of prints:
The overwhelming reasons prints come back are skin tone, under exposure, and contrast. Choosing a broad color space hurt—not helped—the return rate and was responsible for 5% of returned prints.
The big surprise is not even large prints bound for museums or photography exhibits had issues with resolution or compression.
There are help sections for most problems in the chart below, including skin tone, too red, and too blue.