I recently wrote about how good design embraces constraints. In the comments, Kelly asked how we should go about focusing a client on the possible design constraints upfront in the process. This is a good question, and the extent to which you can identify all the constraints upfront depends on the extent to which you are looking to improve the existing offering, or you are looking for a breakthrough.
In my experience, if you are looking to improve on an existing offering, the real constraints typically consist of tangible boundaries that are easy to identify. These would be things like current manufacturing processes, distribution channels, category definition, and organizational structures. If the new design needs to fit within these constraints, the designer should be made aware of them in the beginning. It is then part of the designers job to creatively work within these constraints. For example, if I am a company that manufactures padlocks, and I am improving my current product, the constraints should be easy to identify.
On the other hand, if you want to develop a breakthrough innovation, it is necessary to understand that one of the most important outcomes of the project will be to indentify the constraints. In this case the real constraints tend to be less tangible, consisting of things like the consumers' culture, and macroeconomic regulations and conditions. Any of the constraints listed above would be self-imposed. Back to the padlock example, if I want to develop a breakthrough innovation, defining my company as a padlock company would be unnecessarily limiting. I could redefine the company as a security company, and a whole world of options opens up. The real constraints for how consumers perceive security would need to be indentified as part of the project, before potential solutions are explored. Once potential solutions are explored and selected, the next set of constraints needs to be defined. These would be things like where, how they will be made, new organizational processes that will be needed, which categories will now define the offering, etc.
The point is that regardless of the type of project you are undertaking, the constraints should be identified before the designer starts designing anything. If we are trying to do something truly new, we should be aware that defining constraints is part of the process, and we should be prepared for the reality that current constraints may not need to be imposed on future offerings.