As your child grows and can begin to understand the connection between actions and consequences, make sure you begin to establish the rules of your family's home. It's important to explain to kids what you expect of them before you punish them for a certain behavior. Explain to him that he will have to help clean the wall and will not be able to use his crayons for the rest of the afternoon. If he crayons on the walls again a few days later, you should remind him that crayons are for paper only and then enforce the consequences. While it's sometimes easier for parents to ignore occasional bad behavior or fail to follow through on some threatened punishment, this risks setting a bad precedent.
Consistency is the key to effective discipline.
It's important for parents to decide together what the rules are and then be consistent in upholding them. At the same time you become clear on what behaviors will be punished, don't forget to reward good behaviors. Discipline is not just about punishment. Parents need to remember to recognize good behavior. This is usually more effective than punishing a child for the opposite behavior - not sharing.