Look at the FAQ at the top of the page :)
There are a lot of good quality foods. My dogs are doing great on Taste of the Wild.
Look for foods that have real meat as the first ingredient, no corn, no ingredients that say "by products" or have vague or unknown origins, like "poultry" or "meat by product meal" or "animal fat" that could be from any number of animals. Ingredients are listed in the order of weight, so listed first = bigger portion of the final product.
Oh, and everything listed before the first "fat" is a main ingredient, everything else is supplementary.