Lets see if I can break this down for you to understand.
Just using one point that you mentioned above, Customer Service. How does one know if the Customer Service is going to be good before hiring a contractor for anything?
Are phone calls returned promptly? Are questions answered straightforward, and in an manner that's understandable? Do you even
feel like there is a commitment to customer service even in the bid/quote stage?
Ask around.... ask coworkers, neighbors, friends, etc. about their experience with the company. Ask for references, and actually follow through with contacting previous customers. Contact the BBB & Angies List.
Does the company even appear to act professional? Are the employees you are dealing with acting professional?
It's hard to quantify emotions and gut feelings, but you get the idea.