SerenaSailor MoonSuper Sailor MoonEternal Sailor MoonPrincess SerenaNeo-Queen Serenity
Serena's first form is, of course, her normal self, how she was reborn on Earth. She is somewhat of a ditz, but has a huge heart, and always cares about her family and friends, even if they mercilessly tease her about her grades.
Sailor Moon is the first form. She shout either, "Moon Prism Power!", "Moon Crystal Power!", or "Moon Cosmic Power!". She recieves her first brooch from Luna, her second from (I think) her real mother, Queen Serenity, and her third appears through her and Darien's love for each other.
Super Sailor Moon is an evolved form of Sailor Moon. When the Holy Chalice appears, it gives Sailor Moon a power-up causing her to become Super Sailor Moon. She yells "Crisis, make-up!" [Japanese only], and evolves from Sailor Moon to a Super soldier.
Eternal Sailor Moon is the final form of Sailor Moon. (Actually, in the manga the final form is Sailor Cosmos, but they changed it in the anime so it wouldn't be so confusing.) She yells "Moon Eternal, make up!" [Japanese only], and of course becomes eternal Sailor Moon.
Princess Serena is Serena in the Silver Millenium, back on the Moon Kingdom. She is the daughter of Queen Serenity and King Kronos.
Neo-Queen Serenity is the future Serena, the Queen of Crystal Tokyo. With King Darien (Endymion) by her side, and her little daughter Rini, they rule in the 30th century.