I worked in a small photo lab (in the days of film), and we take the time to try to understand what the photographer was trying to do in each frame and get the color, perfect exposure and contrast. But often, when I trusted other (large) laboratories with my photos, which were to make corrections (mostly self-correction) and they would looking poop. If a framework intentionally underexposed, had lightening so it was all gray ... looking back cuz greens too purple machine tried to compensate.
I like to have a small selection of printed 4 × 6s and see if they are skilled at interpreting their photos without ruining their artistic intentions. Try to include a lot of different types of photographs: portraits, foliage (color correction more often goes wrong in both) high contrast, low contrast, high-key, low-profile (exposure correction goes wrong in four).