I strengthen mine. I can actually tell a difference. If I tap myself in the jaw with my fist, it feels more sturdy than before And I use a neck harness for the back on my neck, then I'll lay down with my head dangling off the bed/bench and put a towel on my head and put a weight on top of it and act like I'm doing crunches, but with just my neck, then I'll switch over to the side and then other side
I do the neck bridge and rolling back on my head. I also do a bridge where I get in a press-up position but then rest on my forehead instead of hands. For my traps I do shrugs and rear shrugs.
[ame]http://www.youtube.com/watch?v=HTdqV8XkYNo[/ame] I have a york fitness version of one of those at 1:40 and out all the biggest weights from a set of dumbells, I used to use it quite a bit, and it definitely makes a noticable difference in neck strength within a month or 2