An extended and higher level writer's checklist used to foster autonomy in the students as well as collaborating with a peer. It also lessens the "crowded teacher's desk" syndrome that often accompanies writing assignments!
I would recommend teaching mini-lessons on all of the checklist categories over time. If students are older, this checklist can be handed out and reviewed in one or two class periods. It can also be printed and laminated for their writing folders or notebooks for reuse.
For classes with iPads, simply download the checklist and students can mark it on individual iPads.