I found this very helpful information about reading a food label at RealAge.com.
I was particularly interested how you can tell if the food probably contains trans fats even if they aren’t listed on the label.
The most nutritional ingredients in a product should be listed first. Read about Ingredients below to learn more.
Do you really know how to read food labels? Deciphering packaging can help you to better control your diet, your nutritional intake, and your serving sizes. Use the following tool as a guide for weight management.

Serving Size
Serving size information is important because the nutritional information provided is based on the serving size. For example, the serving size shown here is three cookies. If you consume six cookies, the nutritional values provided need to be doubled.
The serving size information also helps you decide how much you should be eating.
Calories, Calories from fat
The information in this section of the label helps you monitor the number of calories you take in each day. More importantly, it allows you to make healthy decisions about the foods you eat. Take a look at the number of calories from fat. In this example, 37% of the calories come from fat – anything over 30% is probably too much.
Remember to read the nutrition label critically. Prepackaged or convenience foods may present the nutritional information as “as-packaged” values, so any additional ingredients you need to prepare the food are not included in the information provided.
Total Fat, Saturated Fat
Try to choose products that are low in saturated fats and trans fats, both of which are linked to an early onset of cardiovascular disease. Try to keep your consumption of saturated fat to less than 10% of your daily caloric intake.
Although trans fat isn’t listed on the label, foods containing hydrogenated or partially hydrogenated ingredients contain trans fat, which is known to increase LDL (bad) cholesterol levels. In contrast, foods containing monounsaturated fats, such as olive oil, are actually good for you. To calculate trans fat, add the saturated, polyunsaturated, and monounsaturated fats together and subtract from the total fat. This is likely the amount of hidden trans fat in the food. In this example, the amount of trans fat is 2.0 grams.
Cholesterol
Use this information to reduce the aging of your arteries. Limit your dietary cholesterol intake to less than 125 milligrams per 1,000 calories.
Sodium
The American Heart Association recommends a diet that contains no more than 2,400 milligrams of sodium each day. To reduce the amount of sodium in your diet, avoid high-sodium foods such as processed meats, canned soups, and snack foods such as potato chips.
Total Carbohydrate
When you choose carbohydrates, make them complex. Look for words such as “whole grain” or “100% whole wheat” as the first ingredient on the product label. The words “healthy” or “multigrain” do not necessarily ensure a whole-grain food.
Protein
You can get your protein from animal products, such as eggs, meat, or cheese, or from vegetable sources, such as soy products, nuts, legumes and beans, and seeds.
A diet high in vegetable proteins can help you live longer and younger. By themselves, the vegetable protein sources listed above contain less of a variety of amino acids (the building blocks of proteins) than meats, but when you combine these sources with whole grains such as brown rice, barley, and wheat, all your protein needs can be met.
Although it has not yet been determined scientifically how much protein you need every day, many experts suggest 15% to 20% of your daily calories should come from protein.
Vitamins and Minerals
Here’s the good news! This section of the label gives you the amount of valuable nutrients available. Use this information to compare products
Percent Daily Values
The Percent Daily Value (%DV) makes it easy for you to maintain a balanced diet and to compare different products. Based on a 2,000-calorie per day diet, the %DV bases everything on a percentage. This makes it easy to determine how much of the recommended daily intake of a nutrient is in each serving of food.
Ingredients
Look at the first, second, third, and fourth items in the list of ingredients. If any of the first four are a saturated fat, a partially hydrogenated vegetable oil, a simple sugar, a non-whole-grain carbohydrate, a salt, or a meat, put the item back on the shelf fast.
Also, don’t be fooled by foods that list “enriched” flour. Enriched flour has been milled to remove the bran and wheat germ, which contain the fiber and nutrients. Then it is chemically bleached white. To make sure your food is nutrient-rich, look for products with whole-wheat, whole-grain, or fortified flour, instead.
Just because you don’t see the word ”sugar” on a product’s ingredients list doesn’t mean the food is sugar-free. Sugar comes in many forms, and most of their names end in -ose, e.g., sucrose, dextrose, lactose, maltose, fructose, and glucose. Sugar also masquerades as honey, molasses, and syrup (as in malt and corn syrup), all of which can be very high in calories.