As a component of a short story unit I taught during student teaching, I adopted a writing technique used annually by my mentor teacher: the fast write with story starter. In short, about three times a week, we spent the first 20 minutes of class on a writing activity. We provided the students with 3-4 sentences taken from a variety of novels (the story starters), and the students would chose one and use it as the first sentence in a short story they would write for 10 minutes.
Students were not expected to complete the story, of course, just get as far as they could. After the ten minutes, the students paired up and shared their stories and provided feedback. If time, one or two could be read aloud to the class.This activity not only kept students writing and discussing writing throughout the unit, but also provided a foundation on which they could complete their actual short story assignment at the end of the unit.
Most students enjoyed the activity, so much so that they would ask when we would be doing the next free write. While many students declined reading aloud at first, even upon their nomination by admiring peers, most eventually became eager readers once we established a classroom culture of mutual respect and constructive criticism. Relating the writing to students' lives and cultures was a big part of this success.