Mulligans
General Mulligans
Aldor Attendant is easily the highest priority. Keep Hand of A'dal with any 1-drop other than pen flinger.
Aggro Mulligans
Curving any 1-drop (preferably Aldor Attendant) into Hand of A'dal forms a solid opener against any deck, and is particularly important vs aggro. Keep Crystology if you already have a 1-drop. Keep Consecration vs board-based aggro such as Odd Paladin, Aggro Druid, and Odd Demon Hunter.
Midrange Mulligans
Midrange decks? In Wild? Seriously?