Most everything has been answered, but I did notice a few things that may be of some help.
A lot depends on the month you go, but one basic principle for staying in Yosemite Valley most anytime is to be ready for anything (freezing weather or a nearly-unbearable hot spell in May, and T-shirt/shorts springlike weather in February, or freezing snow with the roads icy. I tent-camped in Upper Pines one February and biked around the valley in shorts one week, and then returned a week later to chains-required, frozen-river mornings.
The hot showers at Curry are a welcome thing for winter camping, and you should just be able to go in with your own towel at no cost. If bedding or clothing gets wet, there is a laundromat at housekeeping camp, open all year. Instead of sitting around a cold campground in the evening, you can go up to the Lodge food court for a hot meal, then maybe go to one of the free 7-8PM presentations, indoors and warm, and sometimes interesting. Also, the Ahwahnee sometimes has stories around the fireplaces, which is a warm comfortable break from a cold campground (Curry and the campgrounds are what I call the refrigerated section of the valley)
If you're using the shuttle, be ready to wait 1/2 hour...it can get mighty cold standing out there, and you'll want very warm clothes, gloves, hat, etc. The long wait is the reason I sometimes skip the shuttle at that time of year. They do run late enough to get you back to the campground after the Lodge events, and if you tell the driver, he may drive you right up to the campground gate (sometimes they don't go around the Happy Isles loop after dark, so if you tell the driver, they'll get you as close as they can). Bring a flashlight for the walk back to camp.
They sell some stretchy traction devices for your shoes in the various stores there, for around $10, and they're well worth having, as things get icy especially in mornings and evenings. They're good to have for emergency use on a trail too, as there are snowy or icy sections on most all of them, open or not. They're just metal studs embedded in a rubber framework that stretches over the shoe.
Waterproof hiking boots take a lot of the worry about getting your socks wet when exploring, even just walking around the valley area. If you're up early on a cold or snowy morning, take a walk or ride to the lower falls trail loop...you might see the "frazil ice" flow along Yosemite creek, and even if not, it's a nice easy walk in winter before breakfast. I always bring bikes, although in December or January it may not be worth the trouble, but otherwise it's really nice having them for getting around the valley. (it might have looked silly to some, to see our bikes sitting there in the deep snow, but they don't know that the 2 days before we biked around the valley in light clothing and the warm sun having a great time).
Since someone mentioned Curry as an alternative, I should mention that the Lodge also has some great winter rates, but only sporadically, when occupancy is traditionally low, and during the week, seldom on weekends. There are some real bargains in January and February, often with a hot breakfast included, and if you're lucky enough to get a heavy snowstorm, you can then explore and enjoy the beauty without having to worry about the basic stuff...you get cold or tired, you have a warm place to go with food nearby. Just be sure to get up early and get out to enjoy the valley in winter, as the sun will quickly change things. While I love waking up in a tent in fresh valley snow, for the cold winter stays, the bargain prices at the Lodge are pretty hard to resist.
Gary
Yosemite Photo Galleries: http://www.pbase.com/roberthouse/yo