From my experience the most widely supported (geograpghically) teams are Saints, Parra and the Dogs, with Manly and Rooster fans suddenly emerging during winning times.
Manly fans usually admit to being Manly fans just to cause arguments with someone. A Manly fan who remembers Tom Mooney is a rare person.
People who would get married at their local football stadium, or who would wear a replica jumper they knitted would usually be Souths fans. People without dentures are usually Souths fans.
Penrith fans have absolutely no allegience to any former club identities.
Tigers fans usually celebrate hard when Parra lose for some reason.
Plenty of Shire residents are Saints supporters. Seems an unwritten law exists that a Saints/Cronulla fan can't ever have a feeling of interest toward both clubs. Saints fans that I know, oddly, have problems understanding other clubs rivalries.
Souths fans love to buy bumper stickers.
Broncos supporters have funny nativity scenes at Christmas. In the manger sits a very small Wayne Bennet, at whose every curt grumble they worship. If they don't win, it's the ref's fault, and if the ref is above reproach, they blame someone in Sydney.
Warriors fans say 'bro' a lot.
Cowboys fans see an urgent need to buy a stupid hat with every jersey. They also don't know how to be verbal after a win.
Manly fans can carry an argument.
Cronulla fans are similar to Manly fans, except they usually do so with a fake westie accent. I've never seen a Cronulla fan sucessfully bait a Manly fan.
Norths fans were intense, but always respected the opposition.
Penrith jumpers are more popular at Centerlink.
A lot of disabled people support Parramatta.
Bronco fans automatically hate anything to do with ARL, Newcastle or Sydney.