As a maker, and someone who has judged at both the ABS Journeyman and Mastersmith levels, I look at knives in a couple of different ways, depending on the situation. I have a lot of other makers who ask me to examine their knives and give them feedback. The method I use to inspect a knife depends on exactly what the individual asks.
If some says "Will you LOOK at my knives?", I will be as nice as possible, pointing out the major issues, and not mentioning the small things. On the other hand, if someone asks... "Would you CRITIQUE my knives?" I examine the knives as if I were judging them for the JS or MS certification. This means that ANYTHING I see, that could have been done better, is pointed out.
OK, I know that likely wasn't what you were looking for, so I'll give you my input as if I were a customer.... The first thing I look at is the overall design/flow of the knife. Sharp corners and angles are not something that I think looks good on a knife. Do my eyes easily follow the profile of the knife? The next thing I look at is the blade/handle alignment...all too often makers will have an otherwise nice looking knife, but when sighting down the spine from the butt end of the handle, the blade looks like it jogs off to one side or another. This is a direct result of not paying attention when finishing the knife. After that, then I look at the fit and finish. If there are ANY gaps, I would walk away. In my opinion a blade should look like it's growing out of the guard, and likewise the guard should look like it's growing out of the handle. Plunge cuts should be even and equal, and blade finishes should be smooth and even without bumps, dips, or waves. The best tool a person can use to examine a blade, is the way that light reflects off of it.
Finally, I think it's very important to ask questions of the maker, about any concerns you might have with a knife.....something that you think odd, might be there for a reason.