One thing to do is RESEARCH!!! This site helped me a ton with very simple things like the tail types. When I got Fireheart, he was marked as a HM double tail. I had to go up to a worker and tell him that the fish was clearly a crowntail. I saved about $6 on him because I knew my fish!
~ Fireheart ~ Spikefin ~ Male Bettas ~ Dalihla ~ Lizzy ~ Female Guppies ~ Sir ~ Boss ~ G6 ~ Prayer ~ Male Guppies ~ Squirt ~ Male Dwarf Gourami ~ Reginaldo ~ Regilina ~ Strange ~ Stranger ~ George ~ Mystery Snails ~ Zeus ~ Poseidon ~ Hades ~ Hermes ~ Apollo ~ Serpae Tetras ~ Bristol ~ London ~ Beverly ~ Female Platies