Teach Behavior as You Would Content
Would you project the quadratic formula and expect the students to be able to use it to solve problems? No. You would most likely use gradual release as a framework to teach how to apply the quadratic formula.
Why would behavior expectations be any different? I like to refer to them as Positive Behavior Expectations. Take the time to introduce the behavior expectation, invite students to create 3-5 criteria for the expectation, followed with a rationale to support why this expectation is important. Engage students in practicing the correct way to display the behavior and how Not to display the particular behavior. Students love to show off their acting skills. Also, when you practice make sure you hold the students accountable. Have the students redo the skill until they have completed it with near perfection. This also let's the students know you mean business. It's not just words and another "rule" they have to follow.
Consider reinforcing the expectations the following days/weeks as an opener for each class. Reserve 5-10 minutes and have students write the steps or criteria for a particular Positive Behavior Expectation. This will continue to communicate what you believe is important in establishing a culture of community. By having students role play, write the steps, and create posters will reinforce the Positive Behavior Expectations. For more information regarding how to implement the Positive Behavior Expectations, check out my book Keep Calm and Teach https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=victoria+lentfer
Let me know if you have any questions. Thanks!