Proper pruning and tree care, based on scientific/ industry research and Best Management Practices for the health and longevity of the particular species, while reducing hazards, using non-invasive/ spike climbing methods, according to industry standards. These considerations are especially important for species that deal with injury and decay organism poorly. Proper care help a tree to be as healthy as possible, reducing likelihood of secondary disease and pest problems, reducing maintenance costs in the longterm.
On a separate note, for bidding jobs, before and after pictures of your work, in addition to the good and bad pruning/ climbing practices, with resulting wound closure or non-closure, and resulting decay.