APA-style research paper instructions and rubric. It requires students to write out their topic, ask for teacher approval, organize their subtopics, and work on their thesis. I also include 5 points of extra credit if they turn it in a week early. Not only does this help them to not wait until the last minute, but it helps you grade a few before you get swamped!
Regarding page length, I go with word count. I find that they're always trying to change the font or the margins and this way, even if it's not APA, you have a solind basis for figuring out how long their paper is.