price comparison between what they are paying and Plan N -
Everyone does things differently, but I check prices against their CURRENT plan before going any further. If there is little or no savings, I tell them "If you like your plan and want to keep it, I will move on. " Then I ask "Did your agent ever mention plan G (or N if they have G now)? You know there can be significant savings vs your current plan. Why do you suppose your agent failed to mention a way to save money?"
By now I have established credibility when I told them they can't improve on their current plan, but have also created doubt in their mind about their current agent.
If I have their interest my next question is "Are you in good health?". Then we go from there.