Note: We’ve tried to keep this very simple, however if you’d rather just come in talk to us about food labels, please do.
You may think that the food label is just about selling a product, and you’d be half right. Besides marketing the food inside the package, the label's function is to provide some really important information: list of ingredients, guaranteed analysis, nutritional adequacy, and feeding guidelines. 
Food Name
You can do some judging of a food just by its name. For most consumers the name of the food plays an important marketing role. Various rules and regulations regarding pet food and pet food labeling have been established by Association of Animal Feed Control Officials (AAFCO). As you might expect there are rules that determine how the food is named.
    - 95% Rule: If a product contains 95% of a named ingredient (the ingredient's weight includes moisture naturally present in it at the time it's added to the mix), then the label can be named for that ingredient, such as Beef for Dogs. If a product name is Turkey and Chicken for Cats then turkey and chicken together must comprise 95% of the total weight, with more turkey than chicken.
    - 25% (Dinner) Rule: The product must contain between 25% and 95% of the named ingredient, or combination of ingredients, with the predominant ingredient named first, such as Chicken Dinner for Cats. Other words such as platter, entrée, etc., may be used instead of dinner.
    - Flavor Rule: A specific percentage is not required, but the amount must be sufficient to be detected, however, there are no specific testing methods. The word “flavor” must appear on the label and be comparable in appearance to the word describing what the flavor is, such as TOP SIRLOIN FLAVOR Cooked in Savory Juices. Digests are common flavoring agents.
Ingredients List
Rules for listing ingredients are the same as for food intended for human consumption: ingredients are listed in order of pre-processing weight. An ingredient's weight includes the moisture in that food item at the time it's added to the mix, e.g., fresh meat, peas, and apples are heavier than meat meal, pea meal, and dried apples. Look for food with the first ingredients to be the same specified animal protein name on the label, such as duck or beef, not just poultry or meat. And you want to avoid by-products whenever possible. 
Some terms are simply marketing jargon, such as premium and gourmet. Natural has no official meaning, but usually refers to the lack of artificial ingredients. Organic does not yet have FDA rules governing its usage on pet food labels, however, individual ingredients can be listed as organic.
For the best food, treats, and supplements look for all-natural, organic ingredients that are free of GMOs, artificial colors, flavors, and preservatives. Avoid corn, soy, and wheat in any form. Not only are these foods difficult for most dogs and cats to digest, but they are common allergy triggers.
Some food labels tout the presence of wonderful antioxidant ingredients like blueberries and cranberries. Be sure they appear before vitamins and minerals. Lower quality foods masquerading as better foods include those ingredients, but they are near the bottom of the ingredients list.
Guaranteed Analysis
The guaranteed analysis is declared on an “as fed” basis. “As fed” simply means as the food is fed right out of the package. In order to compare wet food to dry food you must convert the guaranteed analyses to dry matter. Dog Food Advisor is a great resource to go to for this. You can also look up most foods at this website and read an analysis of it.
The guaranteed analysis is only part of the nutritional analysis. You also need to consider the quality and bioavailability of the ingredients. Protein can come from a variety of sources besides meat. For example, wheat gluten is primarily protein (21 grams in 1 ounce), but it’s not a high quality protein. Neither a dog nor a cat’s digestive system has the enzymes required to adequately break down and absorb the protein from non-meat sources.
Nutritional Adequacy Statement
Foods that are balanced, complete, or 100% nutritious must meet minimum AAFCO standards. Anything else is meant to be fed as a supplemental food, such as a topper or treat.
Feeding Directions
You may think feeding your furry friend is as simple as scooping out the food, but not all formulas have the same calorie content. One cup of Now Fresh Adult dry food contains 378 calories, but one cup of Now Fresh Small Breed Adult dry food contains 430 calories. Smaller pieces means more pieces per cup!
Some Final Notes
You can feed your dog or cat the most expensive highest quality food available, but if the food doesn’t agree with your pet’s digestive system then try another formula or brand. There are many high quality foods available.
Nutritional needs of dogs and cats are quite different. Food that is balanced and complete for a dog should only be fed to a dog. The same goes with cats. Some foods intended for supplemental feeding can be fed to either. So be sure to read the label.