It's actually pretty easy to plan for a survival situation, start out by making a very short list of the most likely "disasters" that could happen in your area. I live in Metro-Atlanta, so my threats are very similar to anyone elses who lives in a large metro area, here are the most likely in order:
1. Civil Unrest: General disorder, it may be unsafe to go outside due to very small groups of armed, angry people looting. This is most likely to last less that one month, eventually the national guard will show up.
2. Major National Disaster: Flooding, earthquake, tornado, these happen in Georgia all the time, but it's never effected more that one town at a time, any of these will result in looting, but it should stay under control.
3. Terrorist Attack a.k.a. "Man-Made Disaster": Atlanta has multiple military bases and multinational corporations, as well as a hefty population.
4. Zombie Apocalypse: I gotta throw that in there because I am bat-shit crazy.
5. Blue Hat Invasion: To take the US, you have to take Atlanta, Sherman knew it and burned down the city because of it, but like I said, this is less likely than a Zombie Apocalypse.
So what do you need to prepare?
1. Food: Have enough food for you and your family for at least one month, it takes 700 calories a day to not die, but plan for 3000 calories a day. Buy canned food, rice, beans, cereals and canned meats. Buy the stuff you eat on a regular basis. Also buy a case of MRE's, they taste like shit, and make you constipated, keep these around in case you need to take some food with you if you leave your "base camp."
2. Water: Keep at least 2 gallons per person per day for one month, hopefully longer. You can buy 2.5 gallon water containers at Kroger's for around a buck, and they are stackable. You'll need to consume about 1.5 gallons per day for washing dishes, drinking and preparing food, and another 3 gallons per week for bathing.
3. Protection: Buy a handgun and a long-gun. Stick to military calibres with the handgun, 9mm and .45 perform great and have proven themselves over the last one hundred years, but remember, all handguns suck, at least compared to rifles and shotguns. For a long-gun get something common, in a military calibre, stick with 12-gauge, 5.56X45mm, and 7.62X51mm. The Mossberg 590, Remington 870, AR-15, M1A, CETME, or FN-FAL will suite you greatly. Buy your weapons, become proficient in their use and maintenance and then teach all of the other adults in your household how to use them.
4. Communications: Buy a set of two-way radios so that you and your family can communicate. Also get a short-wave radio, either battery or crank operated.
5. Clothing: You need a set of heavy-duty clothing for all members of your house-hold for all the seasons your area goes through.
6. Bug Out Bag: Have a bag prepared with a change of clothing, 3 days worth of food and drinking water, basic survival supplies and tools, extra ammunition, and all of the items necessary to maintain your weapons.
7. Entertainment: you need items to distract you and your family members, this is very important, try to do it without items that take power.
8. Power source: nuff said.
This is a very basic list, and hopefully it will help you be a little more prepared, if you can think of anything that I have missed please leave a comment or shoot me an e-mail and I will at it to the list.