First, parents must learn the sinful patterns of this world. One cannot resist cultural idolatries unless one has learned to identify them. Ah, here's the rub. Second, parents are to help their children think differently from the world. Behavior is based on beliefs.
Beliefs are the rails on which lives run.
Teens must be convinced of their beliefs and their beliefs must be uniquely their own. Beliefs cannot be coerced, only influenced. Thus for parents to gain influence in their teen's life, they must be students of their child's world, as well as an articulate spokesmen of a biblical worldview. Loving persuasion will count more than preachy judgment. More than mere assertions of faith, parents must be able to express why they believe what they believe in a way that is compelling, nonjudgmental, and relevant to their teenager's world.