We mistakenly take evangelism to be manipulation. But that's what the world says. In truth, we're not trying to impose our beliefs on anybody. Biblically, we can't impose our beliefs on anybody. Force and coercion cannot finally bring about the change that God demands. You can't expand Christianity by the sword. Evangelism is not some sort of intellectual imposition. To believe that something is true and to share that with others is not coercion. We don't impose when we evangelize. We freely offer it to all and do not, cannot, force it on anybody.
2) Personal Testimony
A personal testimony is a wonderful thing. The Bible is full of examples of it, and we should testify to the wonderful experience of receiving God's mercy.
But consider John 9 and the man born blind. He gives his testimony but doesn't even know who Jesus is. His words glorify God, but they don't present the gospel. This is not evangelism. Unless you're explicit about Jesus Christ and the cross then it is not the gospel.
3) Social Action / Public Involvement
Mercy ministries display God's kindness, and they are good and appropriate for the Christian to do. But such actions are not evangelism. They may commend the gospel to others, but only if someone has told them the gospel. They need to have the gospel added to them. Helping others or doing our jobs well, whatever they are, in and of themselves are not evangelism.
Apologetics are valuable, but they have their own set of dangers. You can get bogged down in talking about purely intellectual or peripheral matters and never get to the gospel. It's fine for us to talk with unbelieving friends about questions that they have, but our attempts to try and answer them without setting the gospel as the foundation does no good. Jesus must set the agenda for evangelism.
5) The Results of Evangelism
2 Corinthians 2:15 For we are the aroma of Christ to God among those who are being saved and among those who are perishing, 16 to one a fragrance from death to death, to the other a fragrance from life to life. Who is sufficient for these things? Note that the same ministry has two different effects. It's like the parable of the soil: same seed, different results.
We cannot finally judge the correctness of what we do by the immediate response that we get. The need for numbers puts an unnecessary stress on pastors and misunderstands the way that God saves.
We must practice our ministries realizing that some of us will be like Adoniram Judson or William Carey, who had no converts until after seven years of faithful gospel ministry. It's a fact that most people don't believe the gospel the first time they hear it.
Don't let the gospel that you preach be molded by what it is that gets an immediate response. Preach the gospel, trying to persuade--pleading for your hearers to believe--but knowing that you cannot convert a person. And then let God do with it what he will. He alone can call the dead to life. The gospel is powerful, and God is committed to using us to spread this good news.
A summary excerpt of the address Mark Dever gave at the 2009 DesiringGod Conference