Get a neck harness from "Ironmind." They seem to have the best around.
Put the harness on with a moderate amount of weight and perform two different movements.
One for the front of your neck. Do this by lying on your back on a bench head off the end with the neck harness on.
The other movement would be hands on your knees bent over for the back of your neck.
Two sets for each movement.
Don't go all that heavy on these movements for quite sometime. If you do you won't be moving your neck for several days.
Atogether 4 sets, 15 reps per set is plenty!
Do it twice per week and in about 6 months you will have a neck that a gorilla would be proud to own.
Thank me later,