Over prepare for your class. Take time to instruct the class. We all make mistakes but write them down so you can better handle it in the future 

I have learned that usually students behavior is a result to something outside of the classroom. Sometimes if you take the time to talk to your students you cant get them the help they need and that results in better student/teacher relationship. Sometimes there are hard calls to make. Enforcing your classroom rules and polices usually will weed out the unwillingly. 

This course great insight on how to manage different behaviors in the classroom. Having more than one way to do this as well

Clear communication is key. Establish expectations early-not just about rules, but about respect, responsibility, and effort. Let students know what they expect from you as their teacher, and what you hope to see from them as learners. Take time to explain your routines, model classroom procedures, and practice them together.