Buying new instead of used. Talk about a spending leak -- or, rather, a gush. Cars lose 20% of their value the moment they're driven off the lot and 65% in the first five years. Used models can be a real value because you can get a car that's still in fine working order for a fraction of the new-car price. And you'll pay less in collision insurance and taxes, too. Cars aren't the only things worth buying used. Consider the savings on pre-owned books, toys, exercise equipment, children's clothing and furniture. (Of course, there are some things you're better off buying new, including mattresses, laptops, linens, shoes and safety equipment, such as car seats and bike helmets.) Overspending on gas and oil for your car. There's no need to spring for premium fuel if the manufacturer says regular is just fine. You should also check to make sure your tires are optimally inflated to get the best gas mileage. And are you still paying for an oil change every 3,000 miles? Many models nowadays can last 5,000 to 7,000 miles between changes, and some even have built-in sensors to tell you when it's time to change the oil. Check your manual to find the best time for your car's routine maintenance. Keeping unhealthy habits. Smoking costs a lot more than just what you pay for a pack of cigarettes. It significantly increases the cost of life and health insurance. And you'll pay more for homeowners and auto insurance. Add in various other expenses, and the true cost of smoking adds up dramatically over a lifetime -- $86,000 for a 24-year-old woman over a lifetime and $183,000 for a 24-year-old man over a lifetime, according to "The Price of Smoking" (The MIT Press). Using a cell phone that doesn't fit. How many people do you know who have spent hundreds of dollars on fancy phones, and then pay hundreds of dollars every month for the privilege of using them? Your phone is not a status symbol. It is a way to communicate. Many people pay too much for cell phone contracts and don't use all their minutes. Buying brand-name instead of generic. From groceries to clothing to prescription drugs, you could save money by choosing the off-brand over the fancy label. And in many cases, you won't sacrifice much in quality. Clever advertising and fancy packaging don't make brand-name products better than lesser-known brands. When shopping, watch for price discrepancies at the cash register, and make a habit of asking, "Do you have a coupon for this?" You might even be able to haggle for a lower price, especially on seasonal or perishable items, floor models or big-ticket purchases. Many stores will also match or beat their competitors' prices if you speak up. And try asking for a discount if you pay cash or debit -- this saves the store the cut it has to pay the credit-card company, so it may be willing to give you a deal. It doesn't hurt to ask. Being disorganized. It pays to get your financial house in order. Lost bills and receipts, forgotten tax deductions, and clueless spending can cost you hundreds of dollars each year. Start by setting up automatic bill payment online for your monthly bills to eliminate late fees and postage costs. Then get a handful of files to organize important receipts, insurance policies, tax documents and other statements Shopping at the grocery store without a calculator. Check how much an item costs per ounce, pound or other unit of measurement. When you comparison-shop by unit price, you save. For example, if a pack of 40 diapers costs $13, that's 33 cents per diaper. But if you buy a box of 144 diapers for $35, that's 24 cents per diaper. You save 27%! (Of course, buying more of something only saves money if you use it all. If you end up throwing much out, you wasted money.) Paying for things you don't use. Do you watch all those cable channels? Do you need those extra features on your phone? Are you getting your money's worth out of your gym membership? Are you taking full advantage of your Netflix, TiVo and magazine subscriptions? Take a look at what your family actually uses, then trim accordingly. Making impulse purchases. When you buy before you think, you don't give yourself time to shop around for the best price. Take the time to compare prices online, read product reviews and look for coupons when appropriate. Make it a policy to give yourself a cooling-off period in case you're ever tempted to make an impulse purchase. Go home and sleep on the decision. More often than not, you'll decide you don't need the item after all. Dining out frequently. Spending $10, $20, $30 per person for dinner can be a huge drain on your wallet. Throw in a $6 sandwich for lunch every day and you've got quite a leak. Learning to cook and bringing your lunch from home can save a couple hundred bucks each month. When you do go out, consider getting carry-out instead of dining in (you'll save on the tip and drink), skip the overpriced appetizer and dessert, and search the Web for coupons ahead of time.