from the ceiling........lol....sorry couldnt resist.......
the main issue is not to hang it too low....you need a good mounting hook which you can find here:
http://www.titlemma.com/
Also remember that the focal point that you want to hit the bag at is gonna be anywhere from 2 1/2 to 3 feet off the ground depending where your hanging it from
the foot above the ground thing would matter if your trainning low kicks otherwise you prob want it more than 1 ft but my ceiling is 12 ft from the ground......