Their conscience is on your side
The basic concept of the evangelization methods used by Ray Comfort, of The Way Of The Master, is that the conscience of the person to whom you speak is on your side when you are presenting the gospel.
In this interesting video clip, Ray and Kirk talk to a law officer and get some insights into the physical behavior of a guilty person under interrogation. You may notice these same kinds of behaviors when you are confronting people about their sin and their need for a savior.
Remember, while John 3:16 contains an important element of the gospel, it is not the whole “picture.” Without the corollary truths of the following 4 verses, John 3:16 is meaningless.
“…he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil. For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.”