First, consider the African proverb:
It takes a whole village to raise a child.
A great deal of a child's moral development is based on general cultural influence. Living in a gang-ridden high-crime area may lead a child into forming moral judgments based on standards including extreme violence, drug abuse, and abuse of women as "normal." Monitoring peer influences is very important.
Next, parental behavior is important. Children are observant. If you drink heavily, commit adultery, cheat your employer, never donate time or money to charity, etc., your child will probably imitate those behaviors.
Finally, it is important for children to have sustained social contact with adults to internalize the norms of adult morality. This means having family dinners and weekends, rather than just dropping the child in front of television or a computer screen.