Basically, everyone is a member. Members who act helpful, constructive, friendly, or creative can earn that title. Creative mainly comes from the artistic boards such as Creative Art and L&L, just as a side note.
Archknights are selected from this pool of titled members by the head moderator of the board(s) they frequently post in. Then Head Mod discusses the choice with LANDIS, head of the Archknights, and if LANDIS agrees then that person becomes and Archknight for that board.
Moderators are selected from the pool of Archknights that are 18+ in age.
Hope this helps some. ;)