Americans typically throw out 21% of their food, mostly uneaten leftovers and food that has gone bad. That waste costs the average American family of four between $1,350 and $2,275 a year.

To help prevent and reduce the amount of wasted food in your kitchen, here are ways to perform CPR (Culinary Preservation and Resuscitation) on some popular grocery items. These tips work well for us.

AVOCADO

Never put an unripe avocado in the refrigerator, because it may never ripen. But once it is ripe, put it in the refrigerator drawer or vegetable bin and it should stay fresh for about two weeks.

To save half an avocado and prevent it from turning brown, put lemon juice or a thin layer of mayonnaise on the exposed avocado meat and then cover it with plastic wrap. Another option is to put it in an airtight container with a piece of cut-up onion and refrigerate. The sulfur that makes you cry when you chop onions also works as a preservative. Incidentally, it’s a myth that leaving in the pit will help prevent browning—it will prevent browning only on the area directly under the pit.

BAGELS

Bagels last about two months in the freezer. Cut them in half, and wrap each half in plastic wrap before freezing. But don’t microwave a bagel when it’s time to defrost. Microwaving will dehydrate a bagel and make it hard to bite. Instead, warm a bagel in a toaster.

BANANAS

By the time little brown spots appear on the peel, a banana is getting close to being overripe. Put a ripe banana in a plastic bag (with the peel on), and keep it in the refrigerator’s fruit bin. The peel will turn black, but the flesh of the fruit will be fine for several more days. If a banana is too ripe for your taste, wrap it—peel and all—in plastic wrap and freeze. When you’re ready, defrost it and add the flesh to smoothies or pancake or muffin batter or make banana bread.

BEER

Keep beer flavorful by placing cans or bottles upright in or out of the refrigerator. When beer is on its side, more of its contents are exposed to the oxygen in the container. Oxygen depletes the beer of flavor.

COCONUT

To revive shredded coconut that has dried out, let it soak in whole milk for about a half hour. Drain, then spread it out on paper towels and pat dry. You may want to use the leftover coconut-flavored milk when baking or in a smoothie.

CORN

If you buy too many ears of corn, you can freeze them with the husks on. Break off the handle of the corn from the bottom end. From the other end, the top, cut off the flopping-over silk tassels. Place the corn in a freezer bag—about six full-sized ears fit into a gallon-size freezer bag. Once you’ve squeezed out as much air as possible, seal the bag securely. The corn will stay good for up to six months. When you’re ready to have corn, put the frozen ear of corn, husks on, into the microwave and zap it for about four minutes before serving.

COTTAGE CHEESE

Once you have opened a container of cottage cheese, the oxygen layer where bacteria grow is exposed to the air. After you take a portion of cottage cheese, close the container and store it in the refrigerator upside down. That way, you create a vacuum, eliminating most of the oxygen layer and preventing bacteria from proliferating. This upside-down trick will allow the cottage cheese to last an extra week or more. This also works for sour cream.

CREAM

When you have cream left in its container, you can prolong freshness for several days by adding about one-eighth of a teaspoon of baking soda to the container (this small amount will not affect the taste). The baking soda is safe and will neutralize the lactic acid that builds up and causes the cream to sour.

Or you can freeze cream in an ice-cube tray (and use one cube in your morning coffee each day). Once the cubes are thoroughly frozen, you can transfer them to a freezer bag to save space.

EGGS

Keep eggs in their original container. Eggshells are porous, and if they are not in a closed container, they will absorb refrigerator odors. If you go on vacation and want the eggs in the fridge to be edible when you get home, seal the eggs’ pores by coating the shells with a thin layer of vegetable or mineral oil.

FLOUR

If you keep white flour in an airtight container and in a cool, dry place, it will last about 15 months. Whole-grain flours will keep for one to three months. If you want to keep any flour longer, put it in the freezer. When you’re ready to use it, let the flour thaw to room temperature.

LETTUCE, CARROTS, CELERY

Place the limp veggies in very cold ­water with a few slices of raw potato—it shouldn’t take long for them to crisp up. We are not sure why the potato works, but it does!

POTATOES

When you bring potatoes home from the store, keep them in a paper bag and put a small chunk of gingerroot in the bag with them. It will prevent the ­potatoes from sprouting.