Talk to teachers in nearby classrooms prior to class. This can be a big help on your first day as they can give you tips for dealing with students and might even know about the students you'll be overseeing. If you have an issue during school, teachers in neighboring classrooms are a helpful resource; but don't make a habit of peaking your head in constantly. Consult your guidelines first, and then ask for help if you have questions.
Start off with introductions. Provide a few facts about yourself that are child-appropriate -- such as your favorite food or sports you like to play. Have students make quick introductions as well, stating their names and a favorite food or hobby. Another helpful idea is to have students make name tags out of sheets of paper and display them at the front of their desks.
While they aren't small children, fifth graders are still children and as such will get into arguments and misbehave at times. It is important to keep your cool in these situations and avoid yelling or losing your temper, as this can lead to job termination. When you feel your patience slipping, take four or five deep breaths or step out for a second to collect yourself and try and solve the situation in a fair manner following school guidelines.
The ability to discipline will get you far in controlling your class of fifth graders. Address misbehaviors to ensure students know they are accountable for their actions. Again make sure you follow school policy on disciplining. If you begin to feel overwhelmed, ask a school official to come into the classroom and help for a minute. Never ignore bad behavior, as this signals to children they can get away with it and leads to more bad behavior.
Stick to the lesson plan setup for you to ensure kids continue learning at the right pace and subject. Getting off course from topics you are to teach can also lead to termination. If you are an emergency sub and no plan was provided, ask the school's principal for advice and suggestions or ask the students what they worked on the day before.
Enforce the class rules. Read all class rules and have a school handbook at your side. You can add a few basic rules if you don't see them listed, such as no talking unless a student raises his hand; but if the class has been going on a previously set list of rules, use this as a basic guide. Study the rules and school's guidelines so that you aren't constantly looking to them during class.
Prizes can be an added bonus of having a sub for students and can help you win them over. This isn't to say you should bribe the students for respect, but having small prizes like colorful pencils and pens or stickers can give students incentive to be good. Introduce the prizes prior to starting lessons and let students know that their good behavior while their regular teacher is away won't go unrewarded.