Food & Water
Stocking up on canned goods is preferable, since they keep for a long time if not needed (see my post on keeping a rolling pantry). Buy enough bottled water for a gallon of water per person per day. Get one of those "indoor/outdoor" thermometers, and if the power goes out put the outdoor sensor in the fridge. Once the temperature in the fridge is higher than the temperature outside it's time to move the refrigerator food into a secured box outside (watch for predators!), and put the thermometer in the freezer (which will soon become your fridge). For information on keeping food safe in an emergency, see the USDA factsheet. Whether or not water is available or safe during a power outage is very dependent on your circumstances. Find out as much as you can beforehand, but if in doubt boil water before using.
The three most important things are to not set fire to your house, to avoid carbon monoxide poisoning, and to stay warm. Most gas fireplaces will still work in a power outage, but make sure that you have a window open a crack to replenish the oxygen, and make sure you have a Carbon Monoxide detector in the room with the fireplace. Decide which rooms you are not going to use and close the doors. Put blankets up against any place that might cause a draft. You can use a camping stove for a short time to warm drinks and cook food, but they are VERY dangerous so make sure you keep them in a secure place and only use them for short times. Keep dressed in warm clothes at all times: the most important bits of your body to keep warm are the head, feet and hands. Dress in multiple layers to keep warm air trapped. Watch for signs of hypothermia. You probably have a tank of warm water - use it wisely to keep warm!
Other preparation steps
Fill up your car with gas - it can help you escape to a nice warm hotel, can keep you warm (but don't run in the garage), and can be a source of power (especially with an inverter). Get some money out of the bank, since ATMs could be down and cash could be valuable. Check out the frequencies of not just your local radio stations, but more distant ones that may stay up longer. Also, if you have a scanner, find your local ARES/RACES, fire and EMS frequencies at Radio Reference. Charge up everything you might want to use, and keep a supply of AA, C and D batteries on hand.