I talk a lot about consumer insight: how to learn from consumers, how to derive insights, and how to translate them into useful criteria to guide decision-making. I realized that I don't talk so much about how this connects to the design process, and I'll be mixing in more of that from now on.
I've often heard clients talk about holding back on the constraints because they don't want to hinder the creative process. While the intention is good, nothing could be further from the truth. The creative process depends upon constraints. Figuring out how to manage constraints is what creativity is all about. Having a blank slate to design whatever inspires you is what fine art is all about. It may be fun and interesting, but it most likely won't help to achieve your business goals.
Next time you're working with a designer, remember that it's your job to let the designer know about all the constraints to the process ahead of time. Along the way some of these constraints may be challenged or made irrelevant, and that's part of the creative process at work. If you don't do this, the designer will create their own constraints, and what gets designed may not be relevant to your business at all. At that point everyone's time has been wasted.
Also remember that you don't need to decide what the answer is, and have the designer just draw it up and make it pretty. Design is about problem solving. Problem solving needs constraints. Otherwise it's just decoration, and that's a different task altogether.