Yesterday, I posted on the importance of making house calls.  I think that fits in nicely with some things Kathy Sierra has written on the importance of face-to-face interaction.  She summarizes a talk at a recent conference by Dr. Thomas Lewis, a psychiatry professor:

One of the key points he made was that we are fooling ourselves into thinking that text is even half as effective as face-to-face at communicating a message.

[Why?]  We never had to learn to process body language, facial expressions, and tone of voice. We evolved this capability...it's innate. But we had to spend years learning to read and write with any level of sophistication. The brain needs and expects these other--more significant--channels of information, and when they don't come... the brain suffers (and so does the communication). And the problem goes way beyond just an increased chance for misinterpretation.

This is something we all know, but ignore at our peril.  Get off the phone.  Get clients in your office — or go to theirs.  Your message will be better understood in person, you will better connect with your clients, and you will truly hear (and see) what they have to say.