Set standards and limits the first day. Possibly let the pupils help. Put the standards in writing. Learn and use the pupils' names as soon as possible. Pronounce them correctly.
Teacher preparation is critical.
Never discipline one time and ignore the next. Make assignments appropriate for pupils. Recognize individual differences and vary the kind and amount of assignments to keep everyone working to his or her capacity. Maintain a reserve. Do not paint yourself into a verbal corner with too many threats or promises.