Clear expectations, limits and consequences communicated early on and adhered to throughout the year.... consistency with consequences and rewards...give students accountability and involve them in their own management... positive reinforcement, recognize and understand patterns of attention seeking behavior/antecedent/task avoidance attempts, implement planned ignoring.... heavily reward desired behavior, keep logs of student behavior/have a paper trail, include parents in good news about their child (no matter how small) and not only bad news. Keep students busy and task oriented, no idle time, use students as part of the of the class routine. If the opportunity is possible, ask teachers who have had your "problem" students in the past and see what strategies have worked/not worked for them.