Buying things that are not on sale: Most items generally go on sale if you wait for it. Whenever I buy greatly discounted items at a big annual sale like Black Friday, an outlet mall, or on some flash sales site, I wonder why I ever bought items at full-price.
Not preserving your groceries: Even if you're good about saving on your groceries and avoiding the items that are greatly marked up in the supermarket, those savings will be worth less if you don't know how to properly preserve your groceries. If you're throwing away food, you're wasting money. Do things like only cutting fruits and vegetables when you need them, putting your bread in the fridge or the freezer, and making perishable items more visible in your fridge. Here are even more tips for lengthening the life of your groceries.
Never checking your bills for mistakes: Monitor your receipts, bills, and statements to see if there are any mistakes being made. Get into a habit of giving your receipts a quick once-over as soon as you receive them. This may save you money and it'll definitely save you the time and effort of having to go back to the store or calling them to deduct the mistaken charges. Now that big banks are trying to slip in more fees to the unsuspecting customer, you have more reason to monitor your statements. Be a responsible consumer — the sooner you catch on to suspicious fees, the more chances you'll have of getting your money back.
Leaving your electronics plugged in: It's easy to be lazy and leave your electronics plugged in because you figure you'll be using them soon. Electronic items still suck power even when they aren't turned on. In fact, they draw five percent of the energy in American homes, according to a study by the Lawrence Berkeley National Laboratory. The amount of energy wasted is equivalent to the output of 18 power stations!