I think one of the biggest obstacles to people grasping the meaning of the Gospel is that they misunderstand the message. For various reasons, people think what we're offering them is a way to be good enough to go to Heaven. It's the message of every other religion – a system to follow to be moral enough or appease God. It's what has been preached in a lot of purportedly Christian churches.
So if people think we're simply offering our preference for how to be good, it's understandable why they'll respond by thinking any other path is just as legitimate since they also offer a system or code. It's understandable that when we insist our system is the only right system that they think we're narrow-minded.
This is where the Law – the bad news – comes in. It's why the Good News needs to be accompanied by the bad news. It's part of what distinguishes Christaintiy from every other religion. The Law shows us that we are completely incapable of being good enough or appeasing God with our own goodness. We have no goodness. The Law puts to death any hope of being good enough to get to Heaven.
Greg gives an example of how he engages people here.
Once we've given up any hope of being good enough, the central message of Christianity then makes sense to people. Christianity isn't a system, it's a Person. Jesus was good enough on our behalf and makes us righteous enough to go to Heaven apart from anything we can do. Then our exclusive claim that Jesus is the only way makes more sense. It clarifies that we're not offering just another way to be good; we're offering the only Person who can forgive us and make us fit for Heaven.
There are times that we have to work really hard, repeat ourselves, and find different ways of saying the same thing in order to break through the assumptions people have about the Gospel.
I think two simple questions (Columbo-style to elicit information) can be of use sometimes. Years ago I was trained in the Evangelism Explosion method developed by James Kennedy. The two questions are: If you were to die tonight, do you think you would go to Heaven? If you were to explain to God why He should let you into Heaven, what would you say? These questions can help clarify what someone believes about the way to get to Heaven, and helps you address specifically what they believe so you can clarify what the Gospel is so they understand we can't be good enough.