Begin your course by lecturing students on AP style. Make sure all students have an AP Stylebook and gradually work through the book during the semester. Over the course of the class, students should become familiar with all elements of AP style. The AP Stylebook contains guidelines for journalists on grammar, punctuation, proper word choice and usage, capitalization and more. Before asking students to do any copy editing, quiz them to make sure they are learning AP style.
Write a series of news stories that are riddled with errors in grammar, punctuation and AP style. Pass the articles out to your class and have them edit the stories. Grade them on how well they did catching and correcting the errors.
Repeat this exercise frequently. As your students' copy editing skills improve, you can make these exercises more difficult by not allowing them to use the AP Stylebook and thus force them to edit from memory. If your students are taking a reporting class or writing for the school newspaper, you also can have them exchange rough drafts of their own stories and edit each other's work.
Lecture students on the role of content editors. Make clear that content editing is distinct from copy editing. Copy editors correct spelling, grammar and style mistakes. Content editors take a "big-picture" approach, making sure stories are well written and organized, complete, factually sound, based on credible sources and reporting and free of bias.
Write out an example of a poorly written article. Before showing students the article, explain the requirements that the article has to meet for it to be publishable. Discuss the article's potential audience, the question it seeks to answer and its ideal word count. Make sure the story you will be asking them to edit fails to meet at least one of these requirements. For example. give them a book review that is intended for a mass audience but is laced with academic terminology. Students should be able to recognize that they have to simplify such jargon to meet a general audience's needs.
Have students edit the articles. As content editors, their focus should not be spelling or grammar. Instead, they should consider how the article is organized and whether it meets the requirements you have set forth. Their final product may require a great deal of rewriting. If this is the case, you should grade them not only on their editing but also the quality of their writing.
Increase the difficulty of this exercise over time. Present students with as many real-world editorial challenges as possible. For example, assign students articles with factual errors that they must catch and correct. Also, occasionally present students with articles that are beyond the capacity of an editor to fix. Award bonus points to students who recognize that the article must be sent back to the writer for a complete rewrite.