Mike The Machine shows his approach to neck isometrics.
Place in training: at the end of your neck workout
5 sets of 5-10 seconds tension each side
He also answers some common questions on neck training, like fast vs slow tempo.
His favorite neck harnesses are the Spud Inc Super Heavy Duty Neck Harness from ProWristStraps.com and the IronMind Headstrap Fit for Hercules (although he like the shorter chains of the Super Heavy Duty one better).