There are many guides and books about how to spend money, how to buy less expensive things, how to save money. Many of them can miss important things, also many of them may tell about the author’s personal experience and useful heuristics. But what critical thinking can offer if we analyse a situation when a person needs to buy something.
First of all why people buy things? If you want to buy anything you expect that the thing you want to buy has a bigger value for you than the money the thing costs. After the transaction both parties got what they want and probably both would be happier. Here lies one of the problems, impulse purchases: people buy something they like in the moment, that they haven’t planned. So if you want to avoid unnecessary purchases you should plan your shopping trips: make lists, consider different alternatives, look for better places to buy. To avoid impulse purchases of any food I can also recommend to eat well before buying it.
Of course you can visit a shop only to check what you can buy there. Make notes then use the notes to make shopping plans. Read reviews, they can greatly help to choose a better alternative. Also use specialised sites for different goods, for example one can have better reviews of cosmetics, another can have better reviews of food, and so on. It can help you make an informed decision while making a list of things to buy.
Sometimes some goods can look suspiciously cheap. If you think so, check the reviews, look for possible sales event, check the reputation of the reseller and of the producer. You can also check the cost of producing this kind of goods: look for a cost of ingredients or components, for a usual margin on different reselling steps, for indirect costs like the cost of advertisement.
You can also study the basics of marketing to understand how retailers earn their money. It can also help to avoid the same impulse purchases and save time while shopping. For example shop chains can offer discount cards to earn some points to get a discount later. But it is possible that another shop can offer the same product you want at a lower price even considering discounts. Usually discount cards expect you to spend a minimum amount of money to get a discount. As a result you may buy something you really don’t need.
Sellers also use a number of cognitive biases and logical fallacies to advertise and sell more. They can also push your emotions to make the same impulse purchases. There are some examples: the halo effect can be used to connect a fluffy kitten and a lipstick. The urgency effect, sometimes called the mere urgency effect: buy now or the sale will end in a minute. The bandwagon effect: everyone buys and you should do the same. A logical fallacy, the argument from authority: buy this wig because Doctor Luthor wears the same wig.
So the main strategy is to make plans and to rigorously follow them. Use reviews to evaluate alternatives and to make plans. Gather information about different products, shops, and possible options to buy something. Also you can study marketing strategies, study cognitive biases and logical fallacies. You don’t need to memorise all of them, sellers usually use a limited amount. You can also use critical thinking tools to analyse advertisement texts.