One trick to witnessing is to understand that people don’t want to be told anything that they are doing is wrong, and chances are high that you will get some push back, no matter how gentle that you are with your words, but people do love talking about themselves. Instead of pushing them, ask questions like “If you don’t think people should judge others, why are you judging me? How long should a society let another slaughter it’s members before fighting back? (The Crusades)
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Tactics: A Game Plan for Discussing Your Christian Convictions
I highly recommend this book to every Christian out there. If you put this book into practice you will be better able to discuss all touchy subjects, not just Christianity.
Even experts in other areas of Christianity will benefit from this book, it is simple enough that high school students can read it, but has content that even many professors can benefit from.