1) If you are feeding dry, look for source-specific meals to be in the top five ingredients. Meals just mean that the water has been removed from the meat before processing into a dry kibble.
2) Don't be fooled by ingredient splitting. Makers will be sneaky and use differently processed types of the same ingredient to lower its position on the top five.
3) Don't get sidetracked by fashionable ingredients. If you see 'pheasant' or 'quail eggs' in the ingredient list, it's usually halfway down, which mean that there is not a significant amount of that pricey ingredient in there.
4) "By-products" aren't bad. Yes, I know everyone screams that by-products are the trash of the slaughterhouse, but they're wrong. According to the AAFCO, 'By-products' means intestinal tracts, spleens, pancreas, livers, gizzards, hearts, heads, and feet. It does not mean feathers, fur, or hair. These are all things that our little carnivore pets would eat in a natural whole prey diet, and they contain important nutrients (like taurine) that they can't make themselves.
5) Source-specific, source-specific, source-specific. No 'meat' and especially no 'animal'. You want to know the source of the proteins you are giving your pet.
6) These are cats, not people. Cats are obligate carnivores, which means they they are designed to eat nothing but other animals and insects. You want to see high protein and high fat, not low fat. It's better to give less of a nutritionally dense food than to give a lot of food with vegetable fillers. Healthy adult cats should get 15% to 20% of their daily calories from fat, and 30% from animal protein. Since fat is easily and almost completely metabolized, it puts almost no burden on the kidneys. Older cats can get up to 40% of their calories from fat and 15% from animal protein to help relieve pressure on older kidneys. You want to see low carb (5%-10%), though if you feed dry you're not going to get anything less then about 25%.
7) Don't think that 'human-grade' is the only quality worth worrying about - Things that will get a chicken dropped from human-grade to pet-grade can be as trivial as a bruise. I