Inkshedding was first developed by writing teachers Russ Hunt and Jim Reither in the 1980s. You can find all kinds of information about it online. Of course, as with any popular teaching technique, many different practices now fall under the name of inkshedding, as instructors have personalized it and made it their own.
Dan’s version of the technique begins by asking students to spend five minutes writing down their thoughts on the main discussion question for the day. That writing should be what composition teachers call “freewriting” — i.e., the student writes whatever comes to mind, without anyone making judgments about it or corrections to it. Freewriting’s function is to help generate thoughts and ideas, so it’s an excellent starting place for discussions of any kind.
In Dan’s session, the students finish their five minutes of freewriting and then pass their notebooks to another student. Everyone reads the notebook in front of them and then spends five minutes freewriting in response to the first student’s thoughts. That process continues through several iterations, until — after 20 or 25 minutes — the students have engaged in an extended dialogue with each other, all on paper, and are ready to start talking about their ideas out loud. —James M. Lang —Shaking Things Up (Chronicle of Higher Education)
I did a little bit of inkshedding myself when I was in Toronto. My variation is to have students do this on their blogs, on their own time before class starts, so that we can jump right into a classroom discussion. Occasionally I will devote class time to blogging, too, which sends an important signal that I find the activity to be important.