Core77.com has a terrific article by two of my favorite design bloggers Steve Portigal and Niti Bhan on what you need to consider in choosing a design firm (now that everyone knows that design is the differentiator). This is THE piece to read if you are getting into the innovation/design space for the first time--and maybe if you are already in it and want better results.
The article--Shopping for Innovation--starts with a Q&A that captures what design and innovation are all about. Question: How many designers does it take to change a light bulb? Answer: Does it have to be a light bulb? That's it folks--the essence of why design thinking is so essential to innovation and why CEOs and corporations around the world are flocking to design to generate top-line revenue growth.