In all the creative writing classes I've had, we never once discussed imagination.
Some people believe in the muse, some people go through the newspapers for story ideas.
We DID, however, in one of my classes, read a book that relied heavily on practice. In that class, we would read a section of the book and then come to class, where he would have us practice the techniques we had read about in the book. For example, one section of the book would give us fifteen beginning lines, and we would spend the hour writing a story based on one of those lines. If they admit that all it takes is work, they have committed themselves to DO that work. Talk to you later.