One aspect about being a teacher is that you are always teaching. This extends beyond the classroom and often times, beyond the walls of school. Modeling the desired behaviors reminds students of the expectations for all members of the community. Contrast that with having a rule, for example no food or drink in class, that is broken regularly by the teacher arriving with their cup of coffee. What message is received in this case? Rules exist only for some members of the school community? Once you become an adult, the rules don't apply? This disconnect creates a huge challenge for educators as we try to ensure appropriate conduct but don't necessarily display it. Does your staff room operate under the same behavioral expectations and guidelines that you desire in your classroom?
The modeling can take several forms. For example, are you a "Good Morning" person? If this is your normal greeting pattern, then stick to it. Even in those moments where you don't receive a similar reply. For some of our students this is foreign territory. They aren't greeted that way at home or on the street and they aren't quite sure of the right response. If you're only doing it to control their behavior they will sniff out your insincerity and won't respond. If this type of greeting isn't your style, think about how you do acknowledge students. Is it warm and sincere? How do you greet your colleagues? No matter how alone I thought I was I quickly realized my behavior was being watched by many others. The modeling may also be in how you choose to share yourself with your class. One of the best examples I saw of this was with a teacher who brought her "Bag of Me" with her to class. In that large bag were personal items that related to various times in the teacher's life. Students could pick out an item and the teacher then shared the story of why that item was significant. This built a positive relationship and provided a method by which students could also share their stories.
It strikes me as patently unfair to expect that our students will thrive in a world of "Do as I say, not as I do.", and that we would be better served by demonstrating appropriate conduct in an authentic fashion. Remember the eyes are always on you.