Nothing special, really.
Average costume, average wig, average make-up.
Seems like the hardest thing to do would be the eyes, and you can find tons of tutorials exactly like this on youtube, and probably deviantart too.

EDIT: Why was this thread dug up? =\

Hands-down this is my favorite thread on the entire site.She is definitely someone I wanna wake up to in the morning just to see that pretty face of hers.Sailor Jupiter is my favorite though