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, toi pretty much have to ask quizz questions, polls, post links, pictures, vidéos in any club but it also boils down to the popularity of what ever toi post.
toi just have to keep adding good things to the club, such as images, videos, liens and articles. The plus people fan those, the quicker you'll get a medal there. Getting a lot of commentaires 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 votes also helps. Just generally being active all over the club.
The system's a bit random, to be honest. ou it's become aléatoire recently. People get médailles in clubs they've barely been active in, while they're favourite and most active clubs remain medal-less.