Discipline, Don't Just Punish
Punishment is a necessary part of parenting, as long as it's part of an overall discipline strategy. It's one thing to give a preschooler a time out, but quite another for a preschooler to understand why he is getting the time out and what he can do to prevent future time outs. Make sure that punishment is always given in the spirit of education.
At preschool age, your child is learning to gauge the causes and effects of bad behavior. After your child draws on the wall with crayons, for instance, an appropriate response could be to get him to clean up the mess [source: Canadian Paediatric Society: Discipline].
Your preschooler might respond to discipline with some pretty hurtful words (such as "I hate you" or "You're stupid!"). Many parenting experts recommend ignoring it, arguing that your child is simply saying it to get attention. Overreacting to his verbal outbursts in the moment will just reinforce the behavior [source: Fleming].
Be sure to notice good behavior as well as bad behavior. If you can praise good behavior in addition to discouraging bad behavior, the overall effect will be much more potent.
These days, many parenting experts recommend against hitting or yelling at your child. They say spanking or hitting your child teaches him that violence is an acceptable solution to a problem [source: Wallace].
Also, don't resort to trying to shame your preschooler out of bad behavior ("You're making a fool of yourself"). Shaming is a direct affront to a child's emotions and may affect his self-confidence.