NOBODY LIKES A YES MAN
One of the best lessons I learned was ironically from someone I don't respect. We just finished presenting a list of brand names to a client for a new product launch and the client expressed their dislike for a few of the names. As young marketers we were led to believe that the client's always right so of course we reacted like robots and nodded our heads, agreeing with their feedback. But the second the meeting ended we were scolded for agreeing with the client. "We are the experts, not them. That's why they hire us" my boss said. For the first time my perception on the client, agency relationship flipped. I soon realized that openness is key.
I have a theory that there are two kinds of agencies, the "doers" and the "thinkers." The "doers" are agencies that take the safe road. They are reactive and they believe the way to please clients is to do as they say with as little resistance as possible. The "thinkers" are agencies who are more thoughtful in their approach. They question and challenge client briefs to make clients think differently about their brands and their needs.
If you are given the opportunity to share your opinion be honest. To always tell a client that their idea is perfect when that's really not what you believe is not productive. In the end people want to work with people who can offer a fresh perspective on how to improve something. You're an expert, if you want to be.