Many conversations about discontent are about wanting a change in circumstance. An interesting question to consider is what you would do if you got the circumstances you want. What if you had the job/spouse/money/children/travel that you want?
What would you do then? Say all those things are taken care of. What do you spend you time doing then? Where are you looking for fullness of life?
If someone is apathetic about Christ, the root of it is that they don't really believe that he will provide the joy and satisfaction they desire. Most likely they still are looking for that, just in a different place. Where?
You can trace back the specific things you do and care about to figure out where you are truly looking for life.
Listen to people's stories and notice the connections they make. This happened in my life, and then this happened. They may see causation in what is just a coincidence, and that could be a huge part of where they think joy is found or a deep fear.
One of the deepest questions that many others seem to distill to is: what do you really need to be liked and loved?