Get yourself a copy of "Allen & Mike's Really Cool Backcountry Ski Book." Amazon has it. Since you won't be skiing, ignore that, but the rest of the book is full of practical winter camping tips.

Don't assume winter camping is just camping in colder weather-it isn't. Carry more food, fuel and clothes than you normally would. Plan an escape route in case the weather gets unexpectedly bad. If the snow is soft, take snowshoes. You may be able to find rentals somewhere. Going without snowshoes or skis in deep snow is just plain stupid.

Make sure you know how to navigate. If you don't, go with someone who does. Don't rely on a GPS. Batteries go dead, compasses do not.

Check the weather right before leaving.
http://www.nps.gov/grsm/planyourvisit/weather.htm