I have this neck harness
http://i.ebayimg.com/t/HEAD-STRAP-HA...U2w~~60_35.JPG
Got it off Ebay, you attatch weights to the bottom of it, and perform reps, basically nod your head up and down
http://a.espncdn.com/photo/2012/0427..._money_400.jpg
Do not start to heavy, and do not make jerky motions
It's very good