The most important tip is to slow down. That simple act allows the driver to have more reaction time and makes the car handle better.
Avoid cruise control on slick roads or in bad weather conditions.
The less aggressively you accelerate the more chance your tires have of gripping the road. If your car slides off the road, or you are otherwise stranded in the vehicle on the highway it is always safer to stay in the vehicle. Ensure the exhaust pipe is clear, to prevent carbon monoxide from building up in the vehicle, then run the heater from time to time.
If it’s really bad weather, stay at home if you can. The more cars that stay off the road during bad weather, the better ability emergency vehicles and road crews have to move about and get their jobs done.
Always let someone know where you are going and when you are planning on arriving.