Here's my addition to the thread, though Im sure a lot of it has been posted.
I grew up driving in the snow, and actually enjoy it if there arent other people in the way on the road. In high school when fresh snow would fall I would spend my lunch breaks and free periods drifting in the parking lot. I have done some ice racing on frozen lakes and I have driven to and from ski areas countless times(I used to be a ski instructor) in massive blizzards. This is kind of just a jumble of everything I can think of that is relevant, so sorry if some of it is somewhat out of order.
Learn Your Vehicle
The only way to learn how to control your vehicle when it is out of control, is to have practice doing so. It is especially important to know how to correct your vehicle in a slide, as over-correcting can be just as dangerous as the initial skid. So get out in a big empty parking lot when a few inches of fresh snow have fallen and do some donuts, j-turns, and power-braking. Push the car to the edge of control, and then beyond so you know how it feels. Practice hard acceleration and learn to control the fish tails. Practice hard braking to learn how the ABS feels and how to back off of it(read further below). An empty parking lot is a safe place to try this without risking damaging your car or other peoples lives. Just keep your distance from light poles and curbs.
Tires grip much better in fresh snow than on ice or slush. Though you might think its best to stay in everyone elses tracks, it is frequently better to drive on the virgin snow in between lanes or just on the outside of the road. Piles of slush in between lanes are also dangerous, they offset the stability of the vehicle when hitting them at speed, and can send you into a spin.
Some might call me a “hooligan” or something, but I know the limit of my car, and I will drive in the snow/ice as fast as I feel comfortable with it going because I know the limits. But give other drivers their space and dont tailgate. I always leave twice as much space between myself and the car in front of me. Not because I assume they can brake faster than I can, but because I assume the person behind me cant stop as fast as I can.
ABS(anti-lock brakes) engaging are not a bad thing, though if your not familiar it can be scary feeling the pedal shake. ABS senses the brakes locking, and traction/stopping distance is reduced in a skid. Maximum braking is achieved immediately before locking, so ABS is pulsing the brakes between locked and unlocked trying to find the pencil-thin line on the edge of them. If you let off the brakes slightly just so ABS is not engaging, traction will be higher, and stopping distance shorter.
Be extra careful doing down hills, as gravity is against you and the weight of your car. Learn to downshift if your car is automatic to use the engine speed to slow the vehicle down instead of the brakes.
Now a little story to put all these things together. Last winter we had our first real snowfall, and I was a bit stressed out from Finals, work, having just broken up with my girlfriend, so I decided to collect my thoughts over a midnight “Crest Run” to the top of Sandia Peak, a 13 mile long, twisty, hairpin filled, two lane, 3500' ascent past the local ski area to the top of Sandia Mountains. I wasnt the only one up there, there were a handful of trucks and suvs that had the same idea as me, to play in the fresh snow with their cars. On the way up I was having a great time drifting through the corners, watching the speedometer and tachometer spike as I punched it on the straights and all-four light up. On the way down I was being cautious and mellow since gravity was against me. When I would feel the ABS engage I would let off a bit, taking the corners nice and slow. On the 3rd hairpin down I didnt realize I was locking because ABS had not engaged. I began the turn the steering wheel into the corner while still slowing since it was a wide corner and the vehicle didn't respond. I instantly knew that I had been locking the whole time and the ABS had failed. Knowing the limits of the car, I knew I was going way too fast to make the corner, which was a gaurdrail to a cliff dropoff. As I approached the apex of the corner still going too fast, I dropped into second gear, cocked the wheel all the way towards the outside of the corner, and hammered the throttle. This put the car sideways facing the inside of the corner, and I continued to pulse the throttle. As the car began to straighten out at the end of the corner I felt the car kiss the gaurdrail with the back right corner, and then I was out of the corner. I pulled over, fairly shaken, and I saw the ABS light on the dashboard was lit up, indicating it wasnt working. I got out of the car, inspected the damage to the car(not bad considering I could have driven off the mountain), and cautiously drove the rest of the way down the mountain.
Moral of story: Don't place all your faith in the ABS system to work, and know how to control your car. Had I not known how to drift my car around the corner, I would have gone straight off the mountain and probably died or have been severely injured(and not found for a long time).
Have the right Equipment
Summer tires are truly junk in snow, and downright dangerous. Trust me, Ive done it. All-seasons are miles ahead of summer tires when the roads have snow and ice on them, but thats not saying much. Ive done thousands of miles in the snow with all-seasons, but they don't hold a candle to real snow tires. Honestly, I didn't believe the hype, until I tried them. A good set of snow tires is absolutely incredible in the snow.
Chains are Ok(I dont have any experience using them), but think of it this way: with chains you are only gripping when each chain is in contact with the snow. In between each chain row, you are still slipping. With good snow tires, you are constantly having grip, your contact patch of gripping is larger. If your car is FWD, put the chains on the front wheels. If your car is RWD, put it on the rear. If your car is AWD/4WD, and you are hellbent on running chains instead of winter tires, it is best to put them on all 4 wheels. But if you only have 1 pair, put them on the front wheels. This means you will still have drive wheels that have chains, but you will also have the steering wheels with extra traction.
Dont be this guy:
Sand bags in the back of RWD cars and trucks increases the weight/force on the tires, which creates traction. They also come in handy to add traction if you are stuck by pouring sand under the tires. But something most people don't realize if you don't have sand with you, is to use the floormats in your car to get traction as well!
If you know it is going to snow and your car is parked outside, raise the wipers up. When you return to your car, your wipers wont be frozen to the windshield, and it will be easier to scrape snow and ice off them.
Clean all your windows of snow and ice before driving so you can see what is happening around you. And if you have a snow brush/scraper combo, wipe as much snow off the roof, hood, and trunk as you can to it doesnt blow off into cars behind you.
If your defroster can't keep up and your windows are fogging up, crack the window open. It might be cold, but it will help keep the fog down.
NEVER let your fuel tank drop below ¼ tank in the winter, if possible try to keep it at over ½. If you are ever stuck in traffic in a snow storm, it can often take hours to go a few miles, and idling does use fuel.
This is a good start to a “winter emergency gear box” to keep in your trunk. Im not going to include things you should carry in your car year-round such as jumper cables, spare tire, etc.
-Emergency Reflective Blanket
-Bottles of Water
-Entrenchment Tool(aka Fold Up Shovel)
Thats all I can think of for now, if I think of anything else, Ill add it.