You need to consider who will benefit from your service (i.e., your clients), and what their definition is of a quality service. The best way to do this is ask them.

Poll current and past clients about why they like working with you; also ask their opinion on how you might improve your service. These metrics are vital to your path to success as a company. Devise a system of collecting and tracking these metrics so you can objectively analyze your performance. Setting process to for your Business Intelligence metrics.