My Junior year of high school, my English teacher was going over some commonly misused words and got on the subject of "hanged" vs. "hung". She said "When a blanket is clipped to a clothesline to dry, it is hung. When I man is executed by noose, he is hanged. Men are hanged. Men are not hung." My classmate raised his hand and... well, Long story short, my classmate got detention.
The past tense of hang in almost all situations is hung. You hung a picture on the wall yesterday, or you hung out at the mall last week. Only use hanged when referring to someone who has been killed by hanging.