By now, my students know that when it's English class, I don't want to see a single thing on their desks. Not even their English books... I create my own lessons, and only use the prescribed text when absolutely necessary. Absolutely everything must be packed away in their school bags/desks, including pencils, erasers etc... This is one of the most effective rules, because then the children have no distractions (except each other) and have to face the front and pay attention.
I have caught a few students using cellphones in class, and I tell them that if I see a cellphone, I'll use it to call my family in South Africa!
Am I strict? No - not at all. Even if I say so myself ...I would have loved having a teacher like me! During my schooling years, I consider myself extremely lucky to have had some of the best teachers in my life (especially for English & Afrikaans). Perhaps that is where my fondness for languages stems from? And when I think about it, not only were my English & Afrikaans teachers strict, they were passionate about the material they taught.
Another rule in my class is that no Korean is to be spoken in class (except to ask for clarification to the Korean teacher). If i walk around and hear random chatting in Korean, I take points of the student's team. However...if I hear them speak English, I reward them with points.