This is a great lesson plan, also by Lorcher, to implement during the final draft stage of students' writing. Students work collaboratively to assess their classmate's work for errors while putting their proofreading skills into practice at the same time.
Here is a lesson plan that moves beyond examining a paper for grammar and mechanical errors. ELA teacher, Trent Lorcher, teaches students how to edit a paper with the goal of strengthening the main idea in mind.
This lesson, featured on The New York Times' "Learning Network" blog, is wonderfully engaging in building student awareness to grammatical and mechanical mistakes made in writing. Cultivating that awareness to spot mistakes allows students to then assess their own proofreading process.