Love

"A new command I give you: Love one another. As I have loved you, so you must love one another. By this everyone will know you are my disciples, if you love one another." (John 13.34-35)
This was part of the "farewell discourse," Jesus' last instructions to his followers before his Crucifixion. It's interesting that he doesn't lay out some complex evangelistic scheme for how they are going to reach the world with the gospel. He doesn't take the time to lay out a systematic theology for the early church. No! What he says is "love one another." In fact, this will be the mark that shows someone is following Jesus, not fancy church buildings, slick programs, sophisticated theology, or even the number of converts one makes. Love will be the ultimate mark of a follower of Christ.
In deed, a wise teacher told me once that the best evangelism plan was for the church to simply "be the church," which obviously includes love and forgiveness being embodied by a community of faith. This kind of love can only come from the empowering and anointing of the Holy Spirit, who Jesus says God will offer to anyone who asks.
Years ago, the Beatles sang, "Love, love, love, love is all you need!" Try love today. You might be surprised how powerful it is. It is the only thing in the world that multiplies as you give it away!