What type of lock should I get?

I am a real newbie, and I just got my first bike, a Kawasaki Ninja 500. I live in New York and I was wondering if anybody has any suggestion as to what type of lock I should get. I was thinking the benefit of a disc lock would be that it is small (and cheaper, and dollar for dollar harder to break). But with a corded lock I can tie it to an "immovable" object. But from people's experience, which has served them better in the long run? Thanks in advance.