Classroom management importance

I had a terrible time last year in the classroom because of my lack of classroom management skills. I didn't set rules at the beginning of the year, I was only worried about setting a routine, for them to be organized. Routines like, greet me, pray, and pay attention when I'm calling attendance.
The classroom management was one of the topics that I was expecting the most, but I have to admit that I could have been more self-learner. I surrendered to a cruel year with misbehaving students because I didn't do it right since the beginning.
I'll be arriving in Panama on March 9th, that's a week after the class began, and even though I would be a week delay, but certainly I will spend as much time as possible to make sure my students know their rights and duties in the classroom, what it's acceptable or not, and what's behavior will have consequences. I understand that I have to set other procedures like seat arrangement, how to organize groups easily and faster. I have to be able to manage my group in a better standing this year, if not it would in disadvantage again, I will have a mess in the classroom so I can't let that happen.