The usual spelling would be hiragana for the first part and kanji for the second, but the spellings 貴女（方）(if the addressee is female) and 貴男（方）(if the addressee is male) are also in use. On to my question: the spelling 貴方 is more common than either, but then how would you write あなた方? My IME offers 貴方方, but that looks rather clunky. It doesn't offer 貴方々, but I can find examples of that spelling. Would the first or second spelling be more common? (As I've said, the most common is あなた方)
It would depend, but 「あなた方」 would usually be fine. I simplify a bit, but overusing kanji when not needed is not preferable in everyday text. Not saying 「貴方方」would be taken bad in anyway, just have the master nit pickers frown.
This isn't something major or thought about normally, but in newspapers and such, they will usually use
As for 「貴方々」that is most likely a typo, since having 々 after a kanji means repeating that letter, there is a word「方々」, but in this case it's 「貴方」(you)[方](people）