Its very simple: it only works if someone is neutral to you and has a conversation before they go hostile.
after the conversation, pause before he goes hostile and choose
someone who will not be getting into close range (mage/archer) and tell him to talk the the person (still neutral). Let them walk a couple of steps then stop him/her. Now he wont attack until you get him to badly wounded/Near Death as he is waiting for the person to talk to him. Now, dispense of minions, buff and attack, but make sure the conversation person doesnt get into contact with your target (they can do other things, spells, attack minions etc.)
Sometimes it fails (i havent worked out why yet on these rare occasions) but it is great, for kangaxx, other liches and many bosses
sorry if it is already well known but i have never seen it
