The story of how David Wilkerson came to found Teen Challenge should be a must read for anyone who follows Jesus Christ. The Cross and the Switchblade describes how Wilkerson put feet on his faith that took him from rural Pennsylvania to the streets of New York City. It's the story of how a pastor followed the leading of the Holy Spirit and reached out to minister to people with whom the churches would not associate.
Wilkerson describes in his book how essential it is to meet the unloved where they are, rather than waiting for them to show up in church all dressed up and ready to worship within the ranks of the clean and respectable. He also rightly emphasizes the importance of follow up, how one can't just expect to go out and distribute tracts or preach from street corners without also developing real, loving relationships with people and ministering to their needs, both spiritually and physically.
Now that Teen Challenge International has grown to over 200 centers around the world, it is interesting to note that the struggle in recovery ministry continues to be much the same: It's extremely difficult to get people to reach out in love to those who have never been loved, and it's nearly impossible to get church members to venture outside their doors to love their neighbors as they love themselves.