How do we witness?

Any Christian that is worth their salt knows that they are to be salt. He knows that the primary function of a Christian is to "Go and teach." Though most agree on the goal, few agree on the method. Stones Cry Out has a post discussing Korn and P.O.D. One of the members of the rock group Korn has abdicated for personal reasons. In the post, Rick discusses P.O.D.'s love for the Lord. Another blog, Ryan comments, "Let us thank God that he can work through a band like P.O.D. who is popular but has not abandoned God. This is the witness we need to be. We shouldn't shun away from sinners because how can they be reached in a vacuum without God fearing people?"
Though we may not agree on the best methods, we can agree that there are wrong methods. I doubt anyone would propose handing out tracks at a strip club, or placing Bible verses in a Playboy. To become a drug addict to reach drug addicts is a bridge too far. There are methods that are obviously inherently wrong. The question is, where is the line. At what point are Christians wrong and sinful in their methods? Is there a point we actually do more harm than help? If we present people an anesthetized form of the gospel in a secular wrapper, arewe fulling the mandate of "teaching all nations all things whatsoever I have commanded you"?
I am not a fan of P.O.D.'s music. It is loud and obnoxious. That being said, I don't have as much of a problem with their style as with their philosophy. I see them as disguising themselves as the world in order to reach the world. Their purposes are noble, and they presumably are successful at times. We cannot measure the legitimacy of a method by intention or effectiveness. I could reach many people by posting Scripture on a porn site. I may even reach a few people. None of that makes the method Biblically legit. I will not contest whether or not P.O.D. love the Lord, and seek to do His will. Only they can know that. We can only accept what they say.
We need to recongnize the difference between evangelism and entertainment. What may be acceptable for Christians for entertainment may not be acceptable for Christains for evangelism. I can enjoy and be enlightened by a movie that contains violence, foul language, and drug use. I may not be justified in using foul language and drug use to witness to a sailor. The music that P.O.D. plays may not be wrong as entertainment for Christians. But that is not what P.O.D. intends it for. They intend it to be for evangelism. That is why they tour with secular, hard-rock groups.
How should we witness? What should be our methods? What is right and what is wrong? God can work through any method. But that doesn't mean he approves of any method.