FURRIES are best known for dressing up in cute animal costumes. Although, yes, this is a must for being a full-fledged member of the Furry Fandom; the clique actually started with Science Fiction literature. FURRIES give fictional animals human traits: human personalities, human intelligence, the ability to speak and sing, human emotions, and wearing of clothes. The concept was first introduced at a 1980 science fiction convention and the term, "Furry Fandom", was being consistently used by 1983.
HOW TO BE A FURRY: read the work that started it all - Steve Gallacci's, Albedo Anthropomorphics
Come up with your own anthropomorphic character
Buy or better Make an animal character costume
Show off your character - write a comic, a book, go to a party, throw a party, go to a convention, make a short film...