This question has been asked so many times, the answer to this is also listed in FAQ at the bottom of the page. To get a medal, you pretty much have to ask quiz questions, polls, post links, pictures, videos in any club but it also boils down to the popularity of what ever you post.
You just have to keep adding good things to the club, such as images, videos, links and articles. The more people fan those, the quicker you'll get a medal there. Getting a lot of comments on your contributions may also help, as well as starting off forum discussions which get a lot of posts and questions which get many answers. Answering questions and polls also helps. Just generally being active all over the club.
The system's a bit random, to be honest. Or it's become random recently. People get medals in clubs they've barely been active in, while they're favourite and most active clubs remain medal-less.