As CIO one of my key success factor is to choose the good companies to work with.
Based on my experience, the most important criteria is LEADERSHIP.
Leadership to guide me (a customer does not necessary knows what he needs...) Leadership to propose solutions Leadership to take the good decisions to be efficient Leadership to show the direction.
Leadership is the result of companies culture (do they encourage their staff to take risks? ) but depends even more on individuals.
So when I choose a partner I spend quite a lot of time to discuss technical aspects, organisation, schedule, price, but what I'm looking for is to feel if the guys that will lead the project are real leaders!