When my enchanter tries to cast an aura the game says I can't cast it because I don't have enough focus. What the heck is focus, and where do I get it? I'm Lv 78, and I still haven't figured this out.
That means you already have an aura running. I don't recall what level, but eventually you can run two auras as an enchanter. Once that window is filled up you need to cancel it in the aura window (not the song window) if you want to change auras.
I used to see an aura in the song window, but lately I don't. The window is empty and I can't cast one. How do I see the aura window? I didn't know there was one.
It is shift+a by default to open/close the aura window. If you've changed that setting you can get there from the EQ button. From that window you can remove an aura by right-clicking one of the lines.
Auroria Mastery is the AA that allows an additional aura. Even with that, you still need to make a tactical choice as to which two auras to use at any given time http://everquest.allakhazam.com/wiki/EQ:Auroria_Mastery