Rather than thinking outside the box, it is more effective to think inside the box. A semi-structured guideline for initiating the thinking process has an outcome which is more creative and targeted than a random brainstorming process.
Source: Coyne, Kevin P.; Clifford, Patricia Gorman; Dye, Renée
Link: Harvard Business Review; Dec2007, Vol. 85 Issue 12, p70-78, 9p