Lots of good ideas here. Height of the monitor is a big problem. I get pain right at the back of my neck because I can't make my monitor low enough. Also, are you sitting where you're looking straight at the monitor or is your head turned to one side or the other? I've found that if my head isn't straight on, it also causes neck pain. And if your mouse is too far away you can get pain shooting up to your shoulder and into your neck. And, yes, move around a lot. If you can't change the height of your monitor or move your mouse closer (my current problem), get up & walk around, or at least change your position, maybe take a bathroom or drink break (not alcohol while you're working, though!) every hour or so you, that should also help avoid pain. Try stretching every hour. If you really can't leave your chair (or sofa, or whatever) try circling your head around in each direction ten times. This is the biggest help for me. If my shoulders start hurting, I'll raise my arms up over my head, clap my hands, then lower my arms ten times. You can also lift your legs ten times, too, if you get cramps. You do know how to touch type, don't you? I would think that maybe if you don't touch type looking down at the keyboard for the correct letters would cause neck pain, so learn to touch type if you don't already touch type.
And whoever it is who has the Gracie Slick avatar: ALL RIGHT, YOU ROCK! Surrealistic Pillow is STILL my all-time favorite album and the first one I bought on CD (had to special order it and wait nearly a month). I'm actually listening to "Today" right now)