If you're serious about slashing household expenses, it's important to focus on costs you can control. Some items — such as mortgage and utility payments — may claim a large slice of the budget pie, but they're either fixed or relatively inflexible. Banks, for example, expect regular mortgage payments; landlords frown when you don't pay the rent. You can don a sweater to reduce heating costs, but take that approach too far and your family will likely complain. Unless you're willing to watch your lawn turn brown or shower only once a week, a certain level of water usage is probably unavoidable.

By contrast, grocery costs are often more controllable. About 30% of an average American household's monthly budget is spent on food, so careful planning and a little discipline when cruising the supermarket aisles can generate significant savings. Here are four suggestions for taming your grocery bill.

• Avoid prepackaged foods. Bagged salads may save a little time, but they often exceed the cost of individual ingredients. Instead of buying hamburger (or tuna or chicken) helper, purchase the rice separately. Add your own spices and herbs. Make your own "prepackaged" helpers to save time and expense.

• Skip the energy bars. These items are often impulse buys. That's why marketing departments place them at eye level near the checkout stand. Read the label and you may find that your "energy" bar is simply glorified candy, loaded with fat and sugar, and costing a bundle.

• Stock up on coupons. Your mother and grandmother used them, and for good reason. Clipping coupons can make a huge dent in your grocery bill. And these days you can find coupons online, as well as in your Sunday newspaper supplement. Printable coupon sites include Coupons.com and SmartSource.com.

• Use care at the warehouse store. Bulk-purchase stores offer great deals on everything from toilet paper to hamburger to electronics. But buying in bulk doesn't always translate to savings. Consider whether a better price is available at your local supermarket, especially when coupons are available. And don't fall into the trap of buying more than you really need, just because the unit price is cheap. Six months later, when you're throwing away that unused package of freezer-burned chicken, you may wonder whether the "bargain purchase" was really a bargain.