How do you make group norms more effective?

Rick Lent raised a great question about the challenges we face in facilitating meetings. I think it's not enough to set ground rules/norms. I like to ask a group: How will you/we hold each other to these norms? What I'm aiming for is shared leadership and shared facilitation, to build their capacity to monitor themselves - and I love it when someone else makes a process comment, like "I don't think we're clear about how this decision is going to be made", or whatever.  
There are surely other factors that influence whether or not we/ participants, wish to follow the norms - such as, "Am I on board with the purpose of this meeting?" "Do I trust the leader or the group?" "Do I believe that people will carry out the decisions that are made?" As facilitators, we need to address these questions as well, to make this transparent to the group. These are usually unstated thoughts, and part of our gift is to surface the unstated and the undiscussables!