I would create a foundation of basic rules before asking the students for input. I believe that when it comes to rules, if the students themselves have buy-in, they will be more apt to follow and police themselves. This is a far better system than creating a list too long to remember of teacher-imposed rules that students will resent.
A few of my foundational rules would be:
Respect others and their right to be heard and learn.
Come to class prepared and on time.
No use of smartphones except when designated for research.
Learning is everyone’s responsibility.
Here are a couple of useful classroom rule websites: