Testimonies are great things about what the Lord has done for us, but no-one will be offended when you talk about what God has done for you. You need to be specific about sin, about Christ's death on the cross, about others' need for a saviour, and about their need to repent and trust in Christ.
Mark DeverWe can't know at any given time how God will bless our faithful witness. So the apparent numerical growth of the church is never a good guide to how faithful we have been in evangelism.
Mark DeverLet's say you don't want to stress the urgency of the gospel. Imagine that you are a hyper-Calvinist, and you just figure that people's salvation is a matter for the sovereignty of God. Well, if that's the case, there will never be the heartfelt pleading that you would see in a Spurgeon or an Edwards, or in the Apostle Paul where he pours out his heart in Romans 9 and 10 for the Jewish people.
Mark DeverIndeed, some secularists are so worried about Christianity, they think Christians are about as dangerous as Muslim terrorists. They get really worried when we don't invest our lives in this-worldly concerns. They look on us as unpredictable free agents. When we reject their relativism and make absolutist spiritual claims, they look at us as nervously as they would a terrorist with a suicide bomb strapped to his back. Of course, Christians are not into coercion in any form. But it is very hard to persuade secularists of that.
Mark Dever