This tip requires the Covetous Gold Serpent Ring (http://darksouls.wikidot.com/covetous-gold-serpent-ring) and the ability to pass the yellow barriers by placing the lordvessel.
Travel down through the Catacombs & Tomb of the Giants until you reach the entrance to Gravelord Nito. Use a bow to clear the fireball shooting lichs from the area and equip your ring. Now walk in slow circles in the watery area to force the baby skeletons to appear. Try to keep them all in a small group by circling around them then kill them all in one wide swing attack. Grab any Humanity items that appear as quickly as you can as they will disappear after 1-2 seconds.
Once you start obtaining some I suggest you actually consume about 10 humanity in order to further boost your Item Discovery trait to its maximum potential. With this I have actually picked up 2 to 4 humanity from one sword swing + about 1038 souls while playing on NG, not NG+