All dogs are different, so what may work for one, won't work for another. As a dog owner, it is our responsibility to read labels and buy the dog food that we feel comfortable feeding our dogs.
For the best nutrition, look at the first 5 ingredients on the label. The ingredients in dog food are required to be listed in order of weight, so the first ingredient on the list is the one with the greatest volume in the food. Should be a meat source, run away from a food that has corn, or any sort of grain or byproduct in as the first ingredient.
Be wary of labels that contain unidentified “meat” and never a "by-product".
Note also that since the list runs in order of weight, it is better to see “chicken meal” than “chicken” at the top of the list. “Chicken” includes a high degree of water content, “chicken meal” does not, it is weighed after the water was taken out.
For example, “chicken” may be listed first, but after cooking and the water is removed, it may actually be the fourth or fifth ingredient, not necessarily the first as suggested.
Do not forget to look at the preservatives used. Some are carcinogenic(cancerous). Some common cacinogenic preservatives are: BHT, ethoxyquin, BHA and propylene glycol (a less toxic form of anti-freeze). Citric acid as a preservative can also be problematic as it dramatically increases the risk of bloat if the food is moistened before feeding. Look for food using tocopherols, ascorbic acid (The L-enantiomer of ascorbic acid is commonly known as vitamin C.) or anti-oxidants such as rosemary extract. Better yet, purchase a food that doesn’t contain preservatives at all (there are a few).
Some helpful links:
http://www.fuzzyfaces.com/lfood2.html
http://www.flintriverranch.org/dogeatdog.html
http://www.dachshund.org/article_wheres_the_beef.html