From the blog: "Communicating with customers consistently is essential to great customer service. Customers like to be kept in the loop and doing so is important to keeping them happy. With that in mind, companies should make a genuine effort to notify customers before doing something to their account or to anything that affects them.
Contact them through different mediums...
Be clear and honest with timelines...
Communicate what is being done and why...
Be prepared to answer questions..."
Full text and active links are available at the source site listed below.
Source: Service Untitled, 31 October 2008