Be prepared. If you have set activities to implement, there will be less time for the children to disrupt the lesson. Coordinate with the classroom teacher, which allows you to understand what will happen in the lesson and to plan your actions accordingly. Anticipate the questions and queries the children might ask, and plan answers for them. Do not learn things by rote, though, because this will sound false, Keep in mind that you need to be flexible to be a successful classroom monitor.
Act with confidence. Children are instinctive -- they can sense uncertainty or fear and will take advantage if they do not feel you are in control. Ask the classroom teacher if you can lead one lesson a week. This will show the children you are a figure of authority. Plan what you are going to say at the start and end of each lesson, and do not hesitate or stutter. Practice in front of the mirror if you are nervous.
Keep calm. Losing your temper will not help to control the children. Set clear disciplinary practices in place, such as a warning system, which ends in sending naughty children to wait outside. Use the same system as the classroom teacher for consistency. When giving disciplinary instructions, wait for silence and keep your voice low and calm. This change of tone will let the children know they have misbehaved.
Be sensitive. Talk or listen to the children, and understand how each student is feeling each day. This can be something as simple as listening to how they call their name in the morning register. This allows you to identify potentially troublesome children before the lesson starts and to monitor them to prevent disruption.