When Jonas is apprehensive about the Ceremony of Twelve, he discusses his concerns with his parents. They do their best to ease his apprehension by explaining that the elders of the community have their best interests at heart when they choose assignments for the twelve-year-olds. For example, in chapter 2, Father tells Jonas that he wasn't surprised when he got assigned as Nurturer because the elders take into account each child's aptitude and interests when making assignments. This is the best way to ensure that everyone receives an assignment that will not only make them feel productive throughout life, but will also help the community.
The elders also enforce the rules by making public announcements when someone breaks a rule. They alert the community of unscheduled holidays and when people are released. They administer medicine when needed, direct the delivery of food to each dwelling, and carry the authority to make or change rules as needed. However, rules aren't changed very easily. There is a joke that when they wanted to change the bicycle age from nine to eight, the elders would discuss it. The rule never changed, either because the elders couldn't agree, or they simply don't like changing rules.
When a big decision needs to be made, however, that is when the elders consult the Receiver. For example, in chapter 14, citizens asked to have an increase in the rate of births. The elders went to the Receiver for his advice and he was reminded of all the memories about hunger and poverty due to overpopulation. His advice to the elders was not to increase births in the community so that food would not become scarce at a future date. Therefore, the elders are the managers of the community in every aspect of living, from creating jobs and establishing family units to administering medicine, punishments, and releases.
The Committee of Elders are responsible for making all of the decisions in their society. They watch children as they are growing up and decide what assignments to give. Not only do they assign jobs, but they make almost every choice in each person's life: who to marry, where to live, which child to have, even what name a person will have. Whenever the Committee of Elders have difficulty making such a decision, they consult the Giver, who holds all of the memories for all of the people and can inform them of past decisions.