Be inspired yourself. If you're uninspired, think of something to lift your mood - eg, memories, people who inspired you, music, fictional characters. If you're low, don't try to inspire others - it won't work.
Set the mood rather than being led by it. Be more energetic, more controlled, more measured - or whatever you think is needed to establish and maintain an inspirational mood.
Use language that is passionate and expressive. Give answers that provide more than what is needed: 'An excellent book - it was practical as well as an easy read', rather than 'Yes, it was fine'.