I have a set of standard terms for my clients that describes what I'll do. I start my relationship by providing much more explanation of what I've done and why than I will do for long-term clients, with the goal of helping the new client learn to trust my judgment (i.e., that I have reasons for what I'm doing rather than being arbitrary) and feel that they're in good hands. I explicitly remind them that editing is a cooperative and consensual process, and that the goal is to work together, not to play power games over who gets to make the final decision on whether a change is necessary. I emphasize that as the reader's advocate, anything I failed to understand is likely something other readers will also fail to understand; thus, it's better to work together to find a solution we both like than to leave a problem for readers to solve.