It's not easy for me to answer these sorts of questions as it really needs more knowledge about the person themselves. Are they religious in any way? This is important to consider. Can you communicate to them intelligently about life in general? This is also important. Are they so attached to their Dukkha that they just live with that as a self-image, in other words, are they full of self-pity? Because if they are very, very attached to their self-pity there is almost no way you can help at all. Are they mentally depressed to a state where they really need some deeper psychiatric help? Not knowing the answers to these and other questions , makes it difficult to answer such a broad question.
If they actually wish to get out of their Dukkha, that's the starting point. One of our students has done three retreats but really did not feel comfortable trying to explain the teaching. So whenever people asked them about it, they would have the book ready and just say, "Well, here, read this. See what you think, read this first." So sometimes we do not have to say anything; if they do express interest, maybe pass them the book and see what happens.
One woman, a friend of Rosemary's mother, with osteoporosis who was really bent over, was in so much pain that she was taking pain killers basically all day long and she was groggy most of the time. She expressed to Rosemary's mother that she didn't like the loss of her awareness with all these drugs. Rosemary's mother offered her our book. She read as far as the fourth evening, the Unpleasant Physical Sensations technique - and she started doing it. Within only a few weeks she cut her medication in half and she was no longer groggy. She was so happy with it. She never asked us a single question personally. She has felt that what she had read from the book was so great, that it changed her life really. And it certainly had.
So sometimes there is not much that you have to say or can say but sometimes pass them the book, that starts them off. And then if they start asking more and more you can go from there.