One of the fundamental principles of being missional is contextualization. In short, contextualization simply means to take into consideration the context where one lives and serves.
With all the noteriety that missional practitioners serving in clearly post-Christian areas have gained, it seems some, desiring to follow the example of these leaders, all too readily foresake the principle of contextualization.
It is understandable to want to copy the methods and messages of Tim Keller or Mark Driscoll, among others. No doubt there is much to be learned from these guys. But the temptation to copy is really a trap that will lead most of us to ineffectiveness. Those guys serve in New York and Seattle, respectively. What is needed to serve in those contexts is vastly different than what may be needed in Nashville, Birmingham, or small towns like where I live – Bristol, TN/VA. Principles should be benchmarked and translated, not copied. All effective ministry is local.
In the above video Tim Keller offers some helpful thoughts about advancing the gospel in different social contexts.