I have a powerpoint slide entitled "The Virtues of a Writing Centre Tutor" which I show over and over again to our writing mentors. It contains the following bullet points.
•Spontaneity / Reacting to the present situation
•Think of the student more than yourself
These are the essential qualities that a writing mentor needs to bring to every tutorial. There is the danger that as the mentor becomes more experienced and more knowledgeable about teaching and writing, he or she may forget these basics. If so, the experience of both the student and the mentor is likely to be diminished. Beginner's mind - again!