Good question. When people ask what is the most ignored muscle in the body, most people say forearms or calves. I thought I was the only one on this board who did neck work.
Anyway, some gyms will have a neck machine, which I use. That's the first thing to try out obviously, assuming there's one available.
There's another neck exercise you can do at home that football players and wrestlers do, but you have to ease into it. Get down on your knees and put the top of your head on a pillow in front of you. Put your hands on the floor to stablize yourself, and roll your head down on each side as if you were trying to touch your ears to the floor.
When you first start doing this, take it slow. Get your neck used to it. No jerking motions. Just go from ear to ear, putting more pressure as your neck strengthens. As you get stronger, you'll be off your knees and up on your feet, but still using your hands for stability, balance. Give it a try. Good luck bro!