1. Set an amount of money for food purchases and figure a portion of that amount as food you will purchase for your stockpile - say $5-$10 each week. Normally you'll use it for things that are on sale or otherwise a good buy.
If tuna is on sale for 65-cents a can, purchase 6 cans. If you find a good buy on canned/frozen fruit or veggies, use that $5 for those. When flour or sugar is on sale, stock-up using that $5-$10 portion. You'll quickly find you have several months in your stockpile.
2. Avoid purchasing large quantities of one food item with all the same use-by date. Can you realistically use 24 cans of tomato sauce, green beans, corn, (or whatever) within the use-by date time? It's better to purchase a few at a time since there are only two of you. I only purchase foods with a use-by date of 2010 or 2011, now that I have a large stockpile.
Example: Don't buy 12 jars of peanut butter at one time with a use-by date that is 6-months out, if you typically use 1 jar per month. The math doesn't work. You'll end up needing to plan on how to use 2 jars each month, rather than 1 jar.
Stock your shelves so that the use-by dates are in order. I often find peanut butter on sale, but instead of going to the back of the peanut butter, if I check the use-by date, it might end up being #2, not the last one. Check your dates periodically so you use your food in a timely manner.
3. My food budget is $50/week (two adults). I spend $10/week of it for meat and basically purchase foods that are on sale, discounted, clearance and I "shop" for meal planning from foods in storage. I rarely spend my entire $50 and I often don't purchase meat because it's not a "bargain" (I try to keep to $2/pound or lower for meat - or within that $10).
With the accumulated leftover money, I purchase large amounts of grain (I just bought 100# of wheat 2 weeks ago - $43), a year's worth (24#) of a whey-based milk substitute we use instead of store-bought milk (much cheaper), and in October I purchase grass-fed beef from a friend to stock the freezer. I never "borrow" from next week no matter how good a bargain may seem. There's ALWAYS a bargain every week.
4. Stockpile INGREDIENTS, rather than prepared foods - and learn how to make foods from scratch - you'll $ave money.
When you have the ingredients for making biscuits (flour, leavening, milk, sugar, fat), you can use those same ingredients for making muffins, quick breads, tortillas, pancakes, waffles, cake, cookies.... With the same ingredients you can make your own homemade "convenience" foods by making a Bisquick-like baking mix, or a homemade pancake mix for much less than they cost at the store.
As an example: I keep dried tomato powder in my stockpile (
http://www.thespicehouse.com/spices/tomato-powder?gclid=CLiG_L_4p5sCFRAMDQodZRjqRg), rather than cans of tomato paste, tomato sauce, pizza sauce, spaghetti sauce, etc., because I can make all those things in the quantities I need with tomato powder + water, seasonings, and sweetener for a fraction of the price. Add to that dehydrated tomatoes and frozen tomatoes from the garden. That eliminates a large number of cans in my pantry and saves me a pile of money.
5. I also have a budget for non-food items, which is separate from my grocery money. Non-food items are also purchased when I can get the best buy. I stack savings by purchasing when an item is a loss leader or on sale, AND I can use a coupon (hopefully a double coupon), AND I try to find rebates.
6. I purchase Charlie's Soap (
http://www.charliesoap.com/) for our laundry. A 5-gallon bucket (1280-loads) will last us at least 3.5 years. LOOK how much plastic or boxes I've saved from the trash by using a product from a bulk amount. Because clothes are soft (there isn't any soap build-up from Charlie's Soap), I also NEVER use softener. Another savings.
7. My bottom line is to buy what you use and use what your buy. After years of doing this, I have 6-12-months worth of general pantry foods, and 1-3-years worth of the "Seven Survival Foods" -grains, legumes, sprouting seeds, sweetener, salt, oil (coconut oil for me), and powdered milk. I also have a large supply of what I call longterm "Emergency Foods", which includes #10 cans of freeze-dried: fruits/vegetables, cheese, meat. Powdered: butter, peanut butter, milk, etc.
I mill my own flour from a large assortment of grains/seeds/beans. Grains, properly stored will keep for decades, while flour has a 6-12-month shelf-life. So keep in mind the shelf-life of foods. If you rarely bake in the summer, try to stock your flour the end of summer and during pre-holiday sales. Enough to see your through March or April. I purchase new-crop nuts after the holidays when they are on sale and store them in the freezer or in vacuum-sealed canning jars (using my FoodSaver). So those are planned large purchases.
8. You may find the information from "Cooking with Food Storage Ingredients" helpful - by Utah State University Extension.
http://extension.usu.edu/cache/files/uploads/Cooking with Food Storage Ingredients 6-07.pdf
http://extension.usu.edu/duchesne/htm/fcs/foodstorage
