Well, lets start with water. It's one of the more important things in my opinion. First off, drink lots of it. Obviously you need more of it when it's hot or when you're exerting yourself but just because its not hot doesn't mean you don't need lots of water. Water good, Dehydration bad.(I saw a guy dehydrated once, his skin was fire engine red and he was mumbling about his head exploding and then he started to puke all over the place and continued to moan in greater agony as his skin turned a deeper scarlet color.) If your urine is yellow or worse, amber, you're not getting enough water. It should be clear. Make sure you always have plenty of water available. Make sure your water is pottable before you drink any, even a sip. Obviously if it's coming from a stream, lake, river, your neighbor's toilet or such it needs to be treated but remember- just because it comes out of a hydrant doesn't mean it's pottable. If there is any doubt do one of the folowing.
A) Treat it with iodine tablets you buy at camping stores and follow the directions exactly. Remeber after the bottle of tablets is opened they expire quickly. Throw away expired tablets. I will warn you the water will taste awful. Pouring the water from one container to another will help somewhat. I'd suggest some type of drink mix like Kool-Aid to disguise the taste, or better yet Tang. Bring your winter boots and play moonwalker while drinking technology from our space program.
B)Run the water through a commercial filter wich is rated to take the bad stuff out. If you want to be hip and on the cutting edge this is the way to go. Be prepared to spend a significant amount of time filtering water, these filters generally very slow. Some filters just take out foul tasting stuff and will let the really nasty microbes right though. Keep in mind that most filters have to be replaced every so often, follow directions.
C) Boil it. this is my prefered method. No icky iodine taste and no expensive gangly frustrating filters and pumps. Start by straining the water through a hankerchief a couple times to get the large sediment out like fish, gravel, turtle poop etc. then bring the water to a roaring boil. Let the water boil for at least a fifteen minutes. Ok now here it that all important step I know you coudn't have figured out on your own, LET IT COOL, trust me, skipping this step is bad. Boiled water tastes rather stale and flat, but iodine tablets are worse. Pouring the boiled water from one container to another will dramatically improve the taste. A small amount of salt doesn't hurt either. (interesting side not stolen from The History Channel, Chinamen were often prefered to work on the transcontinental railroad not only because they would work for lower wages but also because they seemed to get sick less, probably due to the fact that they drank tead which means they had to boil the water before they drank it killing the bugs.)
For the Nuts
For those nutsy people out there who camp in the winter here are some tips for melting snow to drink.
A) don't eat the snow without melting it first. Your body likes to stay around 98 degrees, not 32!
B) Use clean snow. I know you really want to use that lemon flavored stuff over by the bush but it just isn't a good idea.
C) If you have any water put a half cup or so to the bottom of the pan and heat it up before adding snow slowly, if you don't the water will taste scorched. Don't ask me how the hell water gets scroced but it sure tastes that way. Keep in mind it takes a lot of snow to get a little bit of water. When you are hiking periodically add a handfull of snow to your water bottle the water already in the bottle will help melt the snow you add.
Just in case you remembered to duck and cover
In the occurance of a nuclear hollocaust or some other disaster and you are unfortunate enough to live through it and pottable water just isn't around you can kill the nasty bugs. If you're alive they probably made it through ok too. Add one teaspoon of Clorox bleach to one U.S. Gallon of water be sure that your bleach contains sodium hypochlorite at 5.25% and that the rest is water, in other words don't use the lemon flavored bleach either. Only do this if you are desperate, since ingesting chlorine bleach is in general not a terribly healthy thing in the long run.
I understand that treating water is a pain espicially since you drinking so much of it right? good, but don't take any shortcuts. I've never had the misfortune myself of getting sick form bad water but I hear it's more than just a nuisance, and being sick as dog twenty miles to the nearest road and fresh out of toilet paper might not be quite the trip you had planned.