Neil Parmar has a good recent piece on the best ways to bribe your children. Here is one of his points:
In addition to spelling out expectations and agreeing on rewards for specific achievements, surprise them once a while with a special reward for good behavior on a continuing basis. Research on how the brain works shows that children react well to surprises.
An unexpected trip to the aquarium, a local museum or another special experience “can be very motivating to a child,” says Srini Pillay, an assistant clinical professor of psychiatry at Harvard Medical School and chief executive of NeuroBusiness Group, which uses brain science to help children and adults overcome psychological obstacles.
Science has shown that unexpected rewards, especially for younger children, can encourage them to make certain behaviors into a lifestyle. Sometimes when Brett Arrington, who owns a consulting firm, is shopping with his 6- and 9-year-old boys he purchases a toy they really want. Mr. Arrington waits until the boys have been especially helpful—by cleaning up someone else’s mess, for example—then he surprises them with the toy. It “works well because it’s not a promise and can happen whenever and for whatever,” says Mr. Arrington.
The full article is here. It also suggests letting your children choose the reward and “matching gifts,” where you match their contribution toward some good or service, especially as your children grow older and develop some earning capacity.