The product design sprint: a five-day recipe for startups – Jake Knapp/Design Partner, Google Ventures
http://www.designstaff.org/articles/product-design-sprint-2012-10-02.html

Day 1: Understand
Dig into the design problem through research, competitive review, and strategy exercises.
Day 2: Diverge
Rapidly develop as many solutions as possible.
Day 3: Decide
Choose the best ideas and hammer out a user story.
Day 4: Prototype
Build something quick and dirty that can be shown to users.
Day 5: Validate
Show the prototype to real humans (in other words, people outside your company) and learn what works and what doesn’t work.