Just like individuals with longer limbs, those with "longer" necks need more isolation work, in addition to all the standard staples.
Olympic lifts are great neck and trap builders, as well as shrugs and direct neck exercises.
Also, it seems the neck responds well to a higher frequency of training....look at wrestlers and football players, and you could throw olympic lifters in there as well.
chances are if you have a long neck, you have long limbs, and thus would have a more ecto'ish body type. This means you need to eat A LOT to grow. Start with that.