Basically, por being an active member of a club and contributing things which others like: 1. Getting the links, articles, imagens and vídeos you've added fanned 2. Answering lots of questions, pesquisas etc. 3. It's easier to get medals in mais active clubes than dormant ones.
I don't think there's a set number of fãs or contributions. The system's pretty random. Sometimes it doesn't really make sense.
