Takarazuka Vocabulary
I'm phasing this page out, as now that the Takarazuka Wiki is well established, it does a way better job of keeping up with nicknames and such than I can. Read the Wiki. Everything you want to know is there.
Every kind of fandom has its own special vocabulary and I think Takarazuka is particularly bad. I would say the sources of confusion for new Takarazuka fans fall into three categories:
Specialized Stage Terms and Vocabulary
Words like otokoyaku, musumeyaku, shinjin-kouen, and so on that make sense only to those closely involved with Takarazuka. Even Japanese native-speakers need help figuring these out.
Here is the Takarazuka Wiki's Glossary of Terms
Performer Nicknames
This drove me nuts when I first got into Takarazuka. I barely knew performers by one name and then people would go referring to them as something else! Star nicknames are used by performers and fans alike to show affection and demonstrate a sort of personal connection. (You can see how performers like to call each other by their nicknames in the translations on my Interviews page.)
Where do nicknames come from? Any of a number of places. Sometimes they're obvious and based on the performer's stage name. (“Kurara” for “Emi Kurara.” It should always be so simple.) or real given name (If it ends in “ko,” there's a good chance it's her real name.) Some are more esoteric. For example, Takumi Hibiki got her nickname because she used to always ride her bike to the music school. Her bicycle's brand name? “Charlie.”
The Wiki's Nickname Chart: A-M N-Z
Gratuitous Japanese
By this I mean non-Japanese fans using Japanese to describe things when not talking in Japanese. Since a lot of Takarazuka fans came to it through interest in Japan (be it the language, anime, theater, or whatever) a lot of fans will slip in “show” Japanese for fun or because we're used to using it and forget not everyone can understand us. Thus, someone will be describing a show perfectly normally in English, and then declare that a star was “Sugoi!” (“Incredible!”)
Since a complete glossary of common Japanese words and phrases is a bit beyond me, I suggest a good Japanese language site (japanese.about.com can get you started) and lots of patience. We don't do it on purpose to be annoying, I swear.