Hi Diab,
You made several very important points about being clear on your expectations for students in your classes. You have to make sure there are no misunderstandings in terms of outcomes. One suggestion I would make is that you can solicit input from your students concerning expectations, assignments, projects, etc. through the use of anonymous student feedback. I hand out 3x5 cards and have the students respond to specific questions I ask them about expectations, etc. I have found that this is an excellent way for me to know exactly where my students are in terms of understanding what I expect from them. By being anonymous, the students give their opinions freely and I am able clarify any misconceptions that exist.
The role model aspect is critical. Students can only model what they see be it good or bad. Instructors have to set the example for the field in which they are preparing students.
Gary