How to do it?

I am preaching this coming Sunday on the sending of the 70-they went door to door telling people about the gospel message. I think telling people is the real thrust of the Great Commission and God's call to all Christians. That being said, how does one do that in a secular world? I find myself in a position where that is doubly difficult.

The easiest answer to the question is that we do it by how we live our lives. That is true, but... That seems like the complete easy way. Also, if we are just giving an example without explanation then a big part is lost. It's good to be a good person, but if there's no explanation the why is missing. I think it's in our verbal witness that the why emerges. The Apostle Paul always points back to Christ and his sacrifice. Our good behavior should also point back to that rationale.

So, I find myself in a situation where I don't have the freedom to discuss faith. What's a guy to do?