Lawrence Kohlberg, Ph.D., a longtime professor of psychology at Harvard University, broke ground in 1970 when he asserted that children are not born with intact moral reasoning abilities and only develop these skills progressively as they mature. According to Kohlberg's theory, children in the preschool years are in stage 1 of the preconventional moral stage of development, meaning that they behave themselves, not because they feel guilty, but because an external authority figure has laid down the rules. Understanding a child's behavior from this perspective normalizes what -- from an adult perspective -- may seem like cruel or amoral behavior on the part of small children.
Remind yourself that you cannot expect a preschool child to know the difference between right and wrong. Tell yourself that preschool children lie, for example, not because they are inherently bad but because they are not yet developmentally capable of grasping the difference between what is true and what isn't. Don't read anymore into it than that.
Establish consistently limits, boundaries and consequences for misbehavior. Recognize that, from Kohlberg's point of view, at this age, children's behavior is predominately shaped and influenced by external factors.
Reward good behavior. Rewards are just as motivating for this age group as are punishments. Teach your child to earn rewards by following the rules and establishing a baseline for further moral teachings once your child is developmentally ready. Combine rewards, such as a hug, with material rewards, such as earning a new toy.
Give age-appropriate reasons for following the rules. Tell your child, for example that hitting you or another child is unacceptable because hitting hurts and he is not allowed to hurt someone. A preschool child understands that some actions result in adult or parental disapproval, but he cannot conceive himself that there is anything "wrong" with the action.