In Part 1 of my Harvard iLab lecture series, Startup Secrets: An insiders guide to unfair competitive advantage, I layout one of the first stages of creating a company: defining the value proposition. See the Slides and Video below.
I also recently summarized some of my thinking on this in a VentureBeat article discussing some of the key points to consider. This includes defining the problem to be solved, offering a solution that can be easily adopted, and some of the questions that entrepreneurs need to consider in order to entice customers. The article can be read here: http://venturebeat.com/2012/04/28/killer-value-proposition/.