People that ask me "PC or Mac?" annoy the hell out of me. So I guess it's a good thing they ask - it lets us both know ahead of time that we won't like each other. (Or at least, they usually don't like me after I say 'I don't care' in the most apathetic voice I can muster.)
On-topic, I think it depends on your personality. For example, I find it easiest to come up with sarcastic jokes and comments about shared experiences. Not everybody likes this, but this is fine because I probably won't like them either, and it's an easy way to tell that we're not going to be good friends. On the other hand, if your personality is loving anime, ask about that. If it's video games, ask about that. Develop your own style, your own personality.