Timoty Prestero is the CEO and founder of Design that Matters, a Cambridge-based non-profit that works to improve services for the poor in developing countries.

 An inventor of three cholera treatment devices, and a former Peace Corps Volunteer, Prestero shared his four rules for success at the 2009 Babson Entrepreneurship Forum.

 Rule 1: Under-promise and over-deliver

 Rule 2: Entrepreneurship is more about saying no than saying yes. Figure out who you are and what you want.

 Rule 3: Nobody wants to hear your troubles. Always inspire everyone.

 Rule 4: Ambiguity is death.

- By Andrew Lightman M’11