Be positive, but firm. Don't reinforce the student's bad reputation. Don't make negative comments in front of the class, but do ask him to come and see you. He may need help. Watch for backsliding.
Old habits are hard to break.
Be a resource. Offer or locate additional instruction and materials at an appropriate level. Keep files to help you come up with materials easily. Peer tutors are another valuable tool. Know what other classes and community resources are available to help a student in need.