Revision is one of my favorite things to teach. I love to revise my own writing until I think the flow and rhythm is just so, so no shock there. This actvitity I read in Triggering Town by Richard Hugo, a great book for those of you who like poetry.
We start with the same simple sentence: The old man walked down the road.
From there, we talk about the different ways you can "load" sentences with detail: in the front, in the middle, at the end, giving characterization, describing setting/landscape.
I do this activity on the overhead, and have written two or three examples of each way to load a sentence. Using a blank sheet of paper to reveal on what I want shown, I read each sentence to my students, then allow them time to practice one way of doing it. We share, I give feedback to them as to what I liked, and then we try another way of loading it (if we just did landscape, we do characterization, next).
When we're done, I have them pull a sentence from their writer's notebook, draft book (a spiral bound notebook for just drafting) and try to revise it.
We start small, practice and share. Later, we discuss as a class, me talking as little as possible about why it's important to revise and what it means for our writing and us as writers. It is one of the more fun lessons I teach. I teach before we really get into any big piece because to re-vision our work ("re" meaning: again, a new. "vision" meaning: the power of sight. Something I cover with my kids) is to bring it from a blank sheet with a few words on it, to something that provokes emotion. That, and I'm one of those sick-os who write poetry and fiction in what spare time I have.