When you head into the supermarket, you're unlikely to be focusing terribly hard on the job in hand: you're in a rush, you're distracted, and all you want is to get round and get out. Unfortunately the supermarkets are well aware of this, and have spent millions of pounds working out exactly how to take advantage your lack of focus - and get you to spend more.
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It's therefore vital to be aware of the common mistakes we make in the supermarket, and take steps to protect ourselves against them. You can check out the full list of pitfalls on the slideshow.
Once you know what you're up against, there are five handy steps you can take, which should keep you clear of the most common traps.
1. Start with a list - think about the meals you need to plan for, and check your cupboards. Too many people buy the same things each week, and have a pile of 10 tins of beans in the cupboard.
2. Stick to the list - make firm rules about when you can deviate and when you can't. It's fine if something you use regularly is incredibly cheap (like washing powder) but not if you spot a mulled-wine-flavoured jam and think 'that looks interesting'.
3. Take a calculator - check if you are buying the cheapest brand and the cheapest size. In some cases you'll need your calculator, and in others you'll have to take pre-packaged fruit and vegetables to the weighing scales to be sure, but don't be too embarrassed to check.
4. Consider deals carefully - they're designed to attract us, but it's important to check you need everything in a multi-buy deal, or that it actually constitutes a saving - either compared to the price of the own brand or compared to the usual price.
5. Take a receipt from last week - this is the easiest way to check the usual price of items and spot good deals and price hikes.