Paul's sermon here is not so much "How to become a Christian," as it is "What to do now that you're a Christian." He stresses, as he has done before, that Christians love each other, really love each other. Give money if they need money. Don't seek revenge against those who may have earned it. Live peaceably (I'm relieved to say that he adds, "as much as possible.)
OTOH: One of my all-time favorite Pauline quotes is verse 20. "Do nice things for your enemies; it's guaranteed to drive them nuts."