Red Cross has great information on how to plan for an emergency.
I am on our local disaster team, and have been to many classes on preparedness and emergency management. I am in Missouri--about 100 miles from the New Madrid fault. If we have another earthquake of the magnitude of the one in 1811-12, St. Louis and Memphis will look like New Orleans after Katrina.
I need to be prepared--if that happens, our little county, 90 miles south of St. Louis, won't be reached for weeks, probably. The grocery stores will empty in a day or two--they already look awfully bare the afternoon before a big snow storm is predicted!! And, because of the geology of our area, we may be relatively untouched, and the first undamaged place the refugees from the river bottoms will find.
Earthquakes aside, the tornados and the ice storms knock out power regularly. I have an electric heat pump, so I installed a ventless gas heater--looks like a little woodstove without a chimney, and it keeps me nice and warm. I have enough food in the pantry and the freezer to last a long time--the stuff in the freezer might have to be canned, but I have the supplies and the fuel (and the know-how) to do so.
Water supply--yes, do rotate your water, or set the older water aside for cleaning and flushing toilets, if you have the room. Bottled water has a date on it. There is water in your toilet tanks, and in your water heater--find the tap on the bottom of the heater, now, before you have to find it in the dark!!