When establishing and enforcing rules and boundaries with students, I have found "Polite but firm" a good mantra. You must have and enforce rules so you must be clear about expectations, always remaining a calm force within the classroom. Politely interact with student but be firm about student use of routines, rules and classroom procedures. Follow your schools code of conduct and do not show favorites which can be very difficult but a must. This seems easy but can actually be quite difficult.
