There in an old movie called "The Sixth Sense" that was about a boy who could see the spirits of dead people who didn't know they were dead. His mission, as he said it, was to "help them".
How, you might ask? To realize their state, let go of it, and by so doing, find new life. The famous line from the movie was when the boy told a child psychologist, "I see dead people." He saw people that no one else could.
This idea resonated deeply with many, many Christians, providing a line that they felt should be coming out of the mouths of Christians in real life. Why?
Because Christians are supposed to the ones who see more deeply than others, seeing people's "spirits" - seeing people way that God sees them. Paul captures this idea by saying, "from now on we regard no one from a worldly point of view" in 2 Corinthians 5:16.
But this may be the Bible's most inaccurate verse. If we changed our view of people when we were converted to Christ, many, many more Christians would be on mission to "help them." To help all people to realize their state, let go of it, and by doing so find new life.
To be an evangelist, instead of getting a bullhorn and setting up at the corner, or going out and knocking doors, just start praying that God would change your view of people - to see them like He does. Trust me, you won't be able to stop yourself from noticing more natural opportunities to share the gospel.