save spirit of the dead for  turn before zereks or  ress or bwonsamdi (if you have already put several 1/1's in your deck).  mulligan for albatross, Tol'vir or Vargoth in most cases or Mass Hysteria if facing aggro or Zul'drak if facing another ress priest.    dont be afraid to heal your opponent or his minions for your quest.  your going for the long game.  fill him with 1/1's and you with 1 cost walls.