finding a knife sharpener
If you have forged knives, ask them if they will grind back the bolster so it doesn't make contact with the cutting board. If they don't grind back the bolster go somewhere else. Ask them if they can reproduce the correct angle on the knife? If they say anything other than yes, go somewhere else.
How "picky" depends on you.
Me, I would ask them if they do hand-sharpening with stones. If yes, I would ask them if they can do a 7 degree outside angle/12 degree inside angle, with a 70/30 grind ratio. If yes, I would hand them one of my "junk" knives and ask them to do it for me. I would watch to see if they check for the burr, and how its removed. I would then examine their work for the required specs and see if the grind was nice and even, and then test for sharpness.
Many Sur la Tables offers professional knife sharpening.
I personally am opposed to using electric and manual knife sharpeners because I think they take the curve out of a chef's knife, which is best to keep. I do have and use a Chef's Choice diamond sharpening stone that I use to keep my knives sharped.