Dear all, 
Reference: Lecture Mon 12 Sep 2011 on customer space.
We heard about the 80-20 rule. You may wish to see how Tim Ferriss did it. One day, he called the 80% of companies which did not bring him favourable business and said that he wants to have more focus on what he was doing. Some of them in fact turned around and offered more to him, just to be on his 20% list. 
More on him here: http://www.fourhourworkweek.com/  

Cheers!
Jovin Hurry