Children's curiosity oftentimes challenges me, but in a good way. My daughter asked me last week why we're here, that got me thinking, as in how to explain that to an 8 year old.
I think explaining using circumstances the teenager can relate to makes it easier for them to comprehend or a visual representation of some sort. Most teens tune out after a while and the words you speak fall on deaf ears.
If they have little or no understanding of the fallen state of the world and the need of a Saviour maybe start there, sometimes going back to basics is necessary.
I agree that conviction within the person has to be there.
A scripture comes to mind
1 Cor 2:4-5
And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power:
That your faith should not stand in the wisdom of men, but in the power of God.