"In my own experience, the best projects I've worked had a clear and open line of communication between the outsourcer and the customer. Both show give and take and both feel comfortable picking up the phone at any time to tackle an issue head-on."
Some will call this communication, but to even have what may seem like the simple concept above(which is no walk in the park to do) a company has to have a culture where it's important for its people, their own, and their customers to know where they stand on an issue, and expect to always know where they stand. In the services business I am - this is customer experience, in a software application they would call the software is easy of use, and in the restaurant business they call this hospitality. For an awesome read on the subject pick up Setting the table by Danny Meyer. I found this book so great that I bet I will be referring to it for quite some time. Earlier in this post I referred to a third book on my streak of good reading lately, well this is it.