Whatever a child finds enjoyable can be used as reinforcement. Being allowed to play with some special toy or game can work well. By observing what a child normally enjoys doing, we can pick reinforcers that will be effective for him. Incentives, however, tend to lose their effectiveness if parents keep reminding the child about them. They will then be seen by the child as just another form of pressure to get him to behave as we want.
Parents have to be careful to keep themselves emotionally detached from the situation.
The point system is popular with many parents. When a certain amount of points have been accumulated, the child can trade these in for some prize - anything from a book or small toy to a mechanical pencil. Allow the child to choose the item he wishes. Prizes can be purchased and shown to the child beforehand. The reward can be non-material as well.