Discipline is not the same thing as punishment. Instead, discipline is the process of teaching children how to behave properly. I think that the following things are the most important.
First, effective parents set clear boundaries for their children. Their children know what is acceptable and whatis not.
Second, effective parents are consistent. They do not say one thing and do another. They do not tell their child, for example, that it is time to go and then let their child continue to play. They say what they mean and stick to it.
Finally, effective parents model good behavior. If they want their kids to behave with respect towards others, they behave that way themselves. That way, they show their kids, rather than telling them, how to act.