What are some activities or discussions that can help demonstrate to somebody he has bipolar disorder?

Mood change routine. Ask about how mood changes affect usual routine functions--staying up for days at a time without sleep, not feeling need to eat, being hypersexual, spending too much, taking on too much responsibility, noting increasing anger and impulsivity.
Getting 'loose" I try and demonstrate just how fast the person is talking, at such a rapid , pressured speed as well as notice the way the manic has difficulty staying on track with changing subjects and going off on tangents these are called flight of ideas.