well you have to contribute to a spot in order to get medals.
if you add picks, images, videos, comment, rate, ask quiz questions etc. you will get a medal.at first a dedicated medal, if you keep contributing a die-hard one, and at last a fanatic medal. :P

You need to post things. Actually, it's not just about rating anymore! You need to submit alot of everything. Even Comments and quiz qustions count now. Don't get to obsessed with getting one. I find that everytime I get one is when I've forgotten all about them ;P You can get them for one then more spot, and there is also fanatic and die-hard fan medals which are hugher up and harder to get. :)