Much great information and ideas are in this thread. I dont wish to repost what has already been said so I'll go in a slightly different direction. In preparations I have considered many different scenarios and how they might affect me, my job and my family. Some are easy to mitigate, some not so much. Most things have simple homeade workaround type solutions, some require things be purchased and either built or stored for later. In evaluating these purchases here are the 5 rules I apply to every decision.
1. Keep it simple. When I worked in chemical plants a decade ago it amazed me to see a million dollar an hour operation get shut down for a 50 cent valve. Along the same lines, in my house I have a 40 dollar coffe pot break and not work again due to some gizmo timer that malfunctioned. Every car I have owned with power windows after a few years the motor starts going to shit. The moral being dont buy bells and whistles that will just break over time and leave you without. Get sturdy items with very little to nothing to break. If something does break, simple items are easier (possible) to repair.
2. Scrounge. It amazes me how much crap people buy. An example, I have a problem with people buying fire starting devices. If you have to carry something around for a fire, buy matches. You dont need a 30 dollar magnesium striker when a 50 cent bic lighter will work. Similiarly look around at what you have, it's amazing what items can serve multiple purposes.
3. Avoide impulse buys. I have been doing this for a few years now. When I see some gizmo that catches my eye and I think I want it (be it on the shelf or something on tv), I make myself wait a week or two. If I still think I need it after that I'll buy it. 90% of the time I dont even remember seeing it. Fight that consumer mindset people. Make do with what you have, that's the mindset. My wife is still quite the consumer and even she agrees that this works and is a good idea.
4. Keep the tank(s) full. A few years ago I was at a gas station convenience store and was in line behind a largish woman. She had a coke, bag of ships, some candy and after hearing the total she asked for 4 dollars of gas. I wanted to yell at her, put that crap down and put some gas in your car. Anyway, the point being that when a purchase meets a few conditions load the truck up. If your going to use it anyway, it's not going to go bad if it waits, if there is even the slightest chance of price increasing, and you can afford it without going into debt buy as much as you can. I cant think of anytime in my life where I had a full tank of gas and said to myself I dont know if I am going to use it all.... same with peanut butter, spagetti noodles, water, cough drops, and a million other things that my family will use on a long enough timeline and can easily be stored at my house instead of a store shelf. Keep the reserves full. I even apply this to non preps, anyone else have a stockpile of sandpapers in various grit?
5. Sustainable. This is a goal and not a rule, but where possible I always try to pursue the option that has less dependance. For example, a push mower with circlular blades versus a gas operated mower that requires gas, oil, spark plugs, new pull string every few years. It is encumbered with dependencies and is not sustainable, the push variety will go as long as I have a rock to hone the blades with a few times a year and some oil to keep the axle lubed with. (crushed nuts or even rendered animal fats should work just fine for that). I gave an example, but it's the mindset behind it that I try to adhere to. Sometimes it just isn't practicle tho.