if anyone has any additions/edits to this, plz for to comment.
keep in mind this is mainly about kibble/canned commercial diets and does not cover raw feeding, which is also a valid and very healthy diet choice(when done right). raw diets aren't really my area of "expertise."
specific brand recommendations are towards the bottom.
what i look for in a pet food:
grains- grains are the most common allergy in cats and dogs. grains are completely unnecessary for cats and dogs, as they are both carnivores. they are used as a filler, to bulk out the product and cut down costs, since they are cheaper than meat. the worst grain is corn, and you will find that most really bad foods (like kibbles and bits, etc) are composed primarily of corn. a grain free diet is the best kibble you can get, but you will want to look into high-protein diets as they are inappropriate for some animals (like those with kidney problems). ideally a food will have no grains, or at least they will not be in the top three ingredients. you also want to watch out for a technique called splitting- science diet is a good example. what they will do is split an ingredient into different components, like "corn meal" and "corn gluten meal" to lower the weight of each component and therefore get them lower on the ingredient list. soybeans are also something you want to avoid usually- simply because of lot of bad foods use them to up the protein content of their food. soy protein cannot be utilized by carnivores. solid gold, nature's variety, and innova all make grain free varieties of kibble. or, you can feed raw food, either homemade or storebought.
by-products- some by-products are not bad! normally, a predator will eat most, if not all, of the prey animal. this includes all those yucky parts that you hear about like feet, intestines, etc. however, by-products should not be too high on the list, since they are basically a cheap form of protein, and don't contain all the nutrients a dog needs. i don't mind seeing them after the first 6-8 ingredients, but they should not be above that.
chemicals- BHA and BHT are preservatives commonly found in pet foods. so is ethoxyquin. BHA, BHT and ethoxyquin are approved in pet foods at far higher levels than they are for human foods. they have been found to cause certain types of cancer at high levels. yeah, everything causes cancer nowadays. but these preservatives should be avoided if at all possible.
meat- ideally the food you choose will use only human grade meat, as pet grade meat is 4-D animals- dying, deceased, diseased, disabled. these are basically waste products from human grade meat slaughterhouses, and are therefore much cheaper to use than healthy animals. bad quality foods can also contain packaged expired grocery store meat, euthanized animals from shelters, biohazardous waste products (tumours, etc), and waste sludge/grease from grease traps. meats should always be the first, and hopefully first three, ingredients listed. never ever buy foods that just say "meat," "meat meal," or "meat and bone meal." you always want to see a specific listed meat/meat meal i.e. "chicken" or "lamb meal."
the benefits of good food:
animals fed high quality food will eat less, since they are able to get more nutrients from the food they are eating. their stools will be smaller, harder, and less smelly. their coats will be shiny and soft, their breath better, and they will have more energy. their teeth will be cleaner (though dental care is still important) and decay will happen at a slower rate. they will generally be healthier and less prone to being overweight.
solid gold ('barking at the moon' is grain free)
nature's variety (also makes raw food + grain free kibble called 'raw instinct')
flint river ranch (mail order only)
natural balance (has many varieties for allergies)
canidae/felidae (best for the lowest price)
chicken soup for the dog/cat lover's soul
innova (especially innova evo, their grain free food)
california natural (basic ingredients for sensitive stomachs)
(these are just suggestions, use your own judgement when reviewing ingredient lists)
foods that pretend to be good but really aren't too great:
royal canin (apparently human grade meat, but too many fillers)
nutro (nutro isn't awful, if nothing else was available i would feed it, but it's pricey for what it is and has lots of grains and other fillers)
foods that are just garbage:
anything you can buy in a grocery store
purina, eukanuba, iams, etc
where to buy:
most of these foods are only available at independent pet/feed stores. you can find some in your area using the store locators on most of their websites. you can also buy online. some petcos carry solid gold and natural balance. petsmart carries blue buffalo (it is a petsmart brand).