If you get stuck in the snow and you are in a fairly safe area, dig the snow away from all the wheels. Work slowly and don't over exert yourself.
Put traction pads or pieces of carpeting, or scraps of cardboard under both drive wheels.
Spread sand, rock salt, ashes or kitty litter under the tires. Then gently, keeping your wheels straight, rock the car back and forth by changing from forward to reverse, increasing the distance traveled with each rock. Use gentle accelerator pressure. If your car is automatic, brake when shifting from drive to reverse or vice versa, to avoid damaging the transmission. If you are stranded try to make the vehicle as visible as possible, using flares, emergency flashers or even a scarf or piece of cloth tied to the aerial.
Stay inside your vehicle. It's the safest and warmest place. Run the engine for 10 minutes every hour but keep a window partially open for ventilation. Check to make sure the exhaust pipe is not blocked with snow. Deadly carbon monoxide from the exhaust is odorless.