Many people inexperienced with driving in the snow make a bad habit out of tailing the vehicle in front of them too closely. Like driving too fast, this lessens your reaction time if there's a problem with the vehicle ahead of you and you need to slow down suddenly.
It's recommended that you double (or if you want to be really cautious -- triple) your normal distance between cars, giving yourself a minimum braking distance of six seconds. Put another way, for every 10 mph (16 kph) you're traveling, you should give yourself four car lengths of space. So if you're traveling at 30 mph (48 kph), you should have 12 car lengths between you and the vehicle ahead of you.
You should also be looking ahead for stoplights, stop signs and curves in the road so you can give yourself adequate time to brake or steer around them.