Before starting your car, you should check the tail pipe. Ensure that you do not have any snow covering it. A snow covered tail pipe can be deadly. The gases from the exhaust could kill the driver and passengers.
Warming your car up before you even attempt to move it is probably a good idea. This allows the engine to get into its optimal running condition. This generally doesn't take all that long with modern engines. However, a warm car can melt the snow, so give it some time and you will get some assistance from your car as well.
Get a snow shovel and dig out some of the snow. Take away snow from all sides of each tire to give them a greater chance of gaining traction.
A demanding physical effort is required for this one. Grab a shovel and create a track for each tire to drive upon. Think of the tracks that you drive on when you get an oil change.
If you happen to plan ahead for these things, then you might have some snow melt on you. Throw down handfuls of the melting salt. Cover the sides around the tires with the salt.
Hit the gas slowly; you should feel your car climb a bit, but then you will suddenly feel it stop. The car will rock back down to your starting position. The key to this trick is timing. You must slowly hit the gas, and climb the snow hill. As your car falls back, hit the gas a bit harder. The momentum from the motion of the vehicle should carry you over the snow hill. Turn your wheel slightly as you do this to improve traction.
Another good idea is to chain your tires. Putting a specially made chain around your tires will allow you to cut through the snow. This method of traversing through the snow has been around for a long time.
Be careful with this. Have some people help push your car out of the snow. Accelerate slowly as the car is being pushed for the best results while turning your wheel.
Placing a floor mat in front of the tire will add friction. The reason you can't get out of the snow, is because the tires have nothing to grab onto. A floor mat could provide the necessary friction to escape the snow.
Not enough air in the tires, or too much, will hinder the amount of traction that a car will get in the snow.
When all else fails, just have the professionals help you out.