Victor Lombardi discusses concept design in Digital Web Magazine, pointing out that digital designers should take some inspiration from design processes for ideation and concept generation from the fields of architecture and industrial design. I think the main idea is to learn from the practices and methods from these fields, and use that as inspiration for what might be useful in your concept design practice. That is not to say that every project needs to result in a dozen concepts that need to be prototyped at high fidelity and therefore at significant cost. But by all means it could mean spending more time in ideation, sketching more alternatives, working from various perspectives and constraints and lack of constraints, and re-framing the problem/solution space—practices that are inexpensive.
One of the reasons I take such inspiration from Sketching the User Experience is because it is filled with these such examples of concept design from industrial design. The key take away for me from that book is that generating concepts loosely and in volume at the onset in what are noncommital gestures or ideas is probably 80% of the process. The sketch as a tool is the most important part as it relates the designer. On the flip-side, the refined prototype, or multiple and different prototypes as the case may be, is 80% of the importance when it comes to the decision makers and stakeholders who approve the design. So what we're talking about here in terms of concept design for digital designers is front-loading the design process in terms of ideation and concept generation.
Victor continues his investigation into concept design at Smart Experience.