Trans-fat-free: For years, the only way to detect the presence of these bad-for-you fats was to scour the ingredients list for "partially hydrogenated" oil. But as of 2006, when the FDA required trans fat amounts on the nutrition panel, makers of processed foods have worked to eliminate them -- and proclaim their trans-fat-free status on their packaging. "But according to the law, the label can read zero grams of trans fat per serving provided it contains .5 grams or less per serving," says Farrell. If the ingredients include partially hydrogenated oil, watch your serving size.

Natural: When you see the word "natural" on a label, you can trust it means the product contains no artificial ingredients or colors. On the other hand, "natural flavors" listed among ingredients are more mysterious. Most "natural flavorings" are manufactured (as are "artificial flavorings"), using chemicals derived from natural sources (spices, fruits, vegetables, meat, fish or dairy). This term cannot, however, be used as code for monosodium glutamate; MSG must be listed as such on the label.

Allergens: As of 2006, labels are required to list any common allergens such as milk, eggs, fish, shellfish, tree nuts, peanuts, wheat and soybeans. So it takes a lot less work to determine if an ingredient on the label contains an allergen such as gluten.

"-ose" words: Beware of the "-ose." "Anything that ends in '-ose' is an added sugar," says Farrell. If you're trying to limit your intake of added sugars, scan ingredients for words like "fructose," "glucose" or "sucrose."

Fat- and sugar-free: Fat-free and sugar-free follow the same rule as trans-fat-free. A product can contain up to half a gram of fat or sugar per serving while declaring it has none.

"Good source of": Packaging will often claim the food is a "good source of" some vital nutrient (such as fiber or vitamin C). While that seems like a fairly vague classification, it is in fact regulated by the FDA to mean the product contains at least 10 percent of the daily requirement for that nutrient. Don't be led to think that a "good source of calcium" will necessarily provide a whole day's worth -- turn the package around and read the nutrition label to see exactly how much it contains.

Ingredient list: Pay attention to the order (and number) of ingredients listed. "They are listed in descending order, so you want the good ingredients to be in the top five at least," says Farrell. If you see a product touting "contains omega-3s" on the label, but the source of those -- say, flaxseeds -- is low in the ingredients list, chances are you're getting just a trace.