The best answer to a referral trigger that has helped me is a handout. I give a handout that highlights the difference between Medicare advantage vs. Medicare supplement. I give this handout to my clients because it breaks down the fundamental differences in coverage options. 

My client was turning 65 and was overwhelmed with the amount of options he had. This helped ease his mind when selecting the appropriate plan to meet his needs. He never asked this question but providing him the information, it made his experience transitioning to Medicare very pleasant.  He was able to narrow down a plan option after going over the handout, in addition to my answering all of his questions.