h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Try to spot goods in the supermarket which are slightly out of date, as you often could get them for half the original price. Naturally it depends which products are safe to consume after expiration date without getting stomach trouble. Some people are more sensitive than others, as some products are more likely to get bad quickly. See also this article: http://www.h2g2.com/A239005 (someone should have recommended it for the edited version).

Uuh-Ooh, I forgot: Be sure you could consume the aforementioned goods on the day of purchase or on the next day at least. Similarly, if you purchase groceries in bulk to save money, make sure they could be consumed before the expiration date. A long time ago, I read in a magazine that up to 40 percent of all groceries purchased are discarded because they are out of date or could otherwise not be eaten. While I would not recommend to eat orange peel, for instance, I think you could nevertheless optimize your food budget.