Practice what you preach. Your child's best teacher is you, his parent. Role model the kind of behavior you hope to see your child display. If you are trying to teach self-control, but lash out angrily at your child when she misbehaves, she will learn to do as you do, not as you say.
Set consistent consequences for your child's behaviors that demonstrate a lack of self-control. For example, if Sarah takes her sister's toy when she is playing with it, Sarah should be asked to return the toy, and be placed in a timeout. Timeouts should always be equal to one minute for each year of your child's age. If Sarah is 5 years old, she should have a five minute timeout.
Give your child options, and be specific about what behavior you want to see him learn. Following a timeout, focus on the behavior you want to see your child adopt. Ask her, "What could you have done instead?" and/or tell her, "Next time please remember to ask if you can borrow the toy."
Praise your child when he does something that shows you he is developing better self-control. Children are impulsive. Parents and teachers hope to teach them how to think about the consequences of their behavior. When you see that your efforts to teach your child are paying off, remember to let your child know that you are pleased with what he did.
Talk to your child about self-control. If you see a character on television acting poorly, comment to your child about what the character is doing, and how the behavior reflects a lack of self-control. You can also do this in real life situations, such as at the beach, or the park. If you notice someone behaving in a way that demonstrates a lack of self-control, point this out to your child. Discuss what you see, and hear. Ask your child, "What could that person have done instead of...?"
Play games that help build self-control. Games are an excellent, fun way to help children learn new skills. Taking turns, standing in line, or having to wait for a final reward are all great ways to help children learn the art of self-control.