Parents have the responsibility of making sure children are brought up according to the plan of God. Parents have to invest in their children enough time, so that they teach them (children) something everyday. This means that even in the absence of the parent, the child should be able to see the goodness and mercies of God in their parents.
This training should go by age of a child. Always bear in mind that children learn more from what they see you doing, as compared to what they hear you say. However, children should also be trained by instruction. What the parents want done should not be compromised by the child.
Children can also be trained by being given incentives. Growing up, my uncle used to give us monetary rewards for reading books and answering questions on what we had learnt from them. We were encouraged to read more books and get more rewards. This is also known as training by reward.
There are several ways in which children can be trained in all areas of life. And as parents, we have the duty to ensure that our children are well rounded and balanced. They should be trained to take their studies seriously and carry out their chores and all other responsibilities assigned to them. They should also be trained in interaction / social skills, how to make friends and keep them.