I am a parent and a therapist who is not a believer in rewards and punishment as a means of discipline. The reward-and-punishment system does a poor job at teaching kids to be responsible for their own behavior; it makes parents responsible for it. It does not encourage personal decision-making by kids. It reinforces the notion that appropriate behavior is demanded only in an authority figure's presence. Punishment takes away respect and threatens the culprit with a loss of affection and approval. The punishment given is hardly ever related to the "crime."
I strongly favor an alternative called logical and natural consequences. This method encourages kids to be responsible for their own behavior while encouraging them to make decisions about appropriate behavior. Natural and logical consequences allow kids to learn from the natural and social order of the real world. Kids who refuse to eat get hungry. Kids who scream and kick when it's time to go outside to play are given the option to cooperate or show by their behavior that they are not ready to have fun. There's no power game here, the logical consequences fit the behavior and the child can "own" the outcome.
For a superb introduction into the world of natural and logical consequences, read "The Parent's Handbook "by Dinkmeyer and McKay. It provides a more detailed, example-filled account of this disciplining method along with many other parenting guidelines. It's a great learning tool for parents.