This doesn't always work with everyone in every class, but something that I do on day 1 is to begin a discussion on the classroom's culture and expected student and instructor behaviors. This discussion of values and norms sets expectations, and I periodically bring up our day 1 conversation throughout the term if individuals get off track. It seems help to get the students to first discuss in groups what acceptable classroom behavior looks like, then bring together in a class discussion. Instead of me telling them what they need to do, they tell themselves. Doesn't always work, but I have found success with it.