Peer editing can be very ineffective! Try this new approach! After ten years of working with middle school students, I find this approach works better than all others that I've tried!
With editing circles, students choose an editing area in which they are comfortable/proficient. Also, students can focus on one grammatical item at a time...and not become overwhelmed by all the errors that may be present in their classmates' work. Additionally, students take ownership because they are in charge of their chosen task.
The task cards are centered around a fun Renaissance theme....such as the Punctuation Prince/Princess and Spelling Servant.