I thought Carl Valle wrote an excellent blog post a couple days ago titled "What not to Coach". I highly suggest giving it a good read.
I wrote a similar blog post touching on what I felt are some of the important aspects and challenges that are involved in coaching in my position: Quality Control Coaching.
One of the coaching skills that is often mentioned is cuing, which is a primary component of teaching... but something that I think is important to remember is that cuing does not always, nor should it, involve verbalization. The same goes with feedback: it does not always require talking. I've been challenging myself to coach without saying anything, and it's amazing at how effectively (maybe even more so than with words) one can communicate by cutting out the babble... because I think that's often what athletes hear (try reversing the roles sometime; I talked about it with point #2 here). A certain touch, eye contact, body movement or signal can "speak" volumes.
Words can be nice, but can you coach without saying anything?