In Chapter 4 ("Spontaneity") of Impro for Storytellers author Keith Johnstone explains his method of teaching:
I visualize myself as coaxing students away from the rim of a wheel and towards the hub.
This makes a conventional syllabus impossible, since any spoke will do if it enthuses a particular group of students. If a spoke gets boring, I just move to a more interesting spoke. When students reach the hub, all spokes seem equally important and exciting.
^z - 2013-03-17