It is different for all kids, but some kids may need you to be very straight forward with them about the problem. For others, it may only drive them away and cause them rebel against you.
You have to show kids that you understand them, and get a common ground with them before they will even think to listen to you. Do not let them feel attacked when you talk to them because they will be on their guard from the get-go. In casual conversation, bring up things that they listen to, news you have heard, Christian bands they may enjoy. Do not single them out. If all you do is condemn them for things you do not agree with, they will only be more upset. “They will know we are Christians by our love.” Just love your child, and let Jesus shine through you. Offering to buy them a Christian alternative to any of their music might help as added incentive. Free music is always a plus.
My parents never told me I couldn’t listen to any of my music, and I listened to a lot of incredibly vulgar music when I was younger. Be a source of positive feedback in their lives rather than giving lectures, give alternatives. If you want them to “turn away” from something, you have to give them something to turn to.
Check our “Band Charts” for ideas on alternatives.