I have a section of my board dedicated to posting these self-evaluation grades. At the beginning of each class, as I go over the objective, I remind students of the expectations for earning an A. At the end of class, we take 1-2 minutes to self-evaluate using these descriptors. I post whichever grade the class gives itself; 9 times out of 10, my students agree with what I would give them.
This tool also helps redirect students. I can stop class and ask, "What grade would you give yourselves at this point?" I also like to encourage healthy competition between classes by saying things like, "2nd period got an A today... Don't you want to show them that you're just as good as they are?" Sometimes, just having a bad grade from their previous class is motivation enough to improve, or having an A from their previous class motivates them to maintain that grade. You could also use this to build toward some kind of reward at the end of the grading period or year.
Self-evaluating adds a sense of autonomy and responsibility for student behavior. My students were beyond impressed the first time I posted the letter grade they chose without question. They loved having the power to control their "grade" both with their behavior and with their end-of-class reflection. This is one of the most important tools I use in building mutual respect between me and my students.