I think that a classroom, or any group really, runs smoother when expectations are plain. When kids know what is expected of them then they are more apt to act appropriately — and even when there is a laps in behavior with clear rules there is less room for argument. I also really believe in the idea that the teacher should be a model for the behavior expected of their students.
So to develop rules I would keep in mind minimal and to the point, so that students can easily remember and understand them. I would also think about the age of my students and what is commonsense, what will be covered in the student handbook, and ultimately what will make my classroom a good environment for learning.
For instance as a secondary teacher I probably wouldn’t post “Don’t Cheat;’ it should be obvious to students by this age that cheating is inappropriate, and academic honesty is generally covered in student handbooks.
While I would keep my posted rules short and sweet, I would also spend a few minutes at the start of the term going over what they mean in a bit more depth. This would bring them to the attention of the students and allow for any questions or comments to be taken care of.
My four rules would be:
Be Respectful — of yourself, others, and property.
Be Prepared — bring proper supplies and books, finish homework and reading before class.
Do Your Best — be attentive and participate.
Be Relevant — lessons first; discussions of life, the universe, and everything afterword.