I built up a year's supply prior to Y2K (no excessive laughing please) by shopping the discount/sale sections at my local grocery stores. Also, buying specials... canned vegis- 4/1.00... buy the limit, mac-n-cheese- 2/1.00...buy the limit, etc. Basicly, I bought two or three times the food I needed for the week, and put most of it away. It takes a while to build your stock this way, but it doesn't take long, and you start feeling a bit of comfort when looking at your "stash". For those of you who chuckled at the Y2K refference, I've managed to pretty much keep the stock in tact by using up the old (date everything) and replacing it with new, and in the mean time, I'm eating at last year's prices, also, if something happens to my paycheck (how secure is YOUR job), I'm good to go as far as food's concerned for quite a while. Some may see it as paranoia, I call it common sense.
As far as the water issue goes, it will keep in sealed containers quite a while, but it's a good idea to rotate that stock as well. In the past, I've used two-liter, clear, pop bottles, stacked on their side, against one wall of the basement, but have since gone to an out-side cistern and filter system... no need to rotate.
Good luck with your cache, and might I suggest you check out "Backwoods Home" magazine, I think you'll find it an interesting/informative/enjoyable read (no affilliation, just a satisfied reader).

Troy