What is himegyaru exactly?

Himegyaru is about looking like a princess and looking pretty. The word "hime" in himegyaru is the Japanese word for princess. In serious himegyaru it is almost required that you do everything possible to look like a princess. With pretty dresses or tops and skirts, a princess like hairdo (IE: Minibeehives, etc.), pretty jewelry, etc. Heels are almost always requred Casual himegyaru is more lax, you can wear like a pretty cami top with lace or something girly/princess like on it, and a pair of jeans or a regular skirt.

If you are interested in SERIOUS himegyaru, but aren't sure what exactly to do, I recommend that you look at the brand Jesus Diamante. http://www.jesusdiamante.com

If you are interested in Casual himegyaru, I recommend that you look at Liz Lisa and Tralala.
http://lizlisa.com/

Also, try looking at an Ageha magazine or Ageha magazine scans.

Note: Websites are in Japanese but you really need to just look at the clothes.