Ed Stetzer writes an excellent piece on preaching so your audience can hear. He summarizes his thoughts on contextual preaching in this way:
Too often we say, “I want to make the Bible relevant.” No need. It already is. Our job is to present it in ways that help the hearer see that it is relevant—in this and in every culture. We do so by starting at their understanding and taking them to Scripture for the whole answer.
(read the article here)