Sounds like old hat but  anyone wanting to sell in any form should do this:

Examine each photo so closely you get tired of looking at the details. Why?   One example from my experiene is when a customer wanted a particular photo done in bw instead of color.  I did the conversion to be quite pleasing and had the print made.  Oh my..there was a mess up on the print over almost hidng in a corner but therer..rendering that version useless.  I redid, reprinted and the work look fine.

So, what happened?  I had cloned out a section in the original color version.  All blended in quite well and was not seen.  Then, when in bw without color to catch the eyes, the clone work was visible with tell tale traces.  I was surprised and looked at the color vesion...it took very hard looking but traces were there if I knew it look for it.   Slow down, even have someone else look if need be.  You don't want any mistakes showing at all.    

Most of you folks likely pay better attention than I do...but anyway.         Tom