Since I first started working In the industry i had a mentor that would tell me work on every car like your family was going to drive away with it. Every car I work on I ensure the job is done correctly before it is given back to the customer. I currently have all ASE needed for master mechanic.
Quick service, thorough in explaining what was going on even as far as showing me pictures so I didn't have to get under the car to see it myself. His thoroughness was greatly appreciated and service was done quickly and left my ride cleaner than when he started, can't beat that.