Designer Michael Bierut gives a presentation on "Clients." The first part of this (rather lengthy... I fast forwarded some) presentation is about what constitutes "good" and "bad" clients. He makes some insightful points here and exhorts his audience to work hard to vet for good clients. Then, around minute 22, he discusses how to serve those good clients well. I found this the most interesting and instructive portion of the presentation. Although Mr. Bierut is speaking to "physical" designers (e.g. industrial designers, exhibit designers, graphic, etc.), his insights apply well to other professional services.