passionately

Answering to diegocaleiro, I think this is the key. Be passionate about the topics that spark your interest, try to transmit how awesome they are. Often people are more lazy and scared by unknown and possibily complicated topics, but if you manage to make things accessible to them, they will be genuinely interested. Then it's also up to your ars oratoria, of course. I have a weird sense of humor and tend to interject the more serious discussion with jokingly remarks, this helps releasing the pressure if the topic gets too complicated.