What things (good or bad) should I look out for when picking out dog/cat food? I do know to look out for meat byproducts and (for cats at least) ground corn, but what else should I look out for? Thanks.

(Just wanting to know the basics)
Here is a complete list that explains why you don't want certain things in your pet food
The Dog Food Project - Ingredients to avoid
Compare these two foods and you will see immediately why one is a better food.
Kibbles 'n Bits
Ingredients: Corn, soybean meal, beef and bone meal, ground wheat, animal fat (BHA used as preservative), corn syrup, wheat middlings, water sufficient for processing, animal digest (source of chicken flavor), propylene glycol, salt, hydrochloric acid, potassium chloride, caramel color, peas, sorbic acid (used as a preservative), sodium carbonate, minerals (ferrous sulfate, zinc oxide, manganous oxide, copper sulfate, calcium iodate, sodium selenite), vitamins (vitamin E supplement, vitamin A supplement, niacin supplement, d-calcium pantothenate, riboflavin supplement, pyridoxine hydrochloride, thiamine mononitrate, vitamin D3 supplement, folic acid, biotin, vitamin B12 supplement), choline chloride, calcium sulfate, wheat flour, carrots, green beans, titanium dioxide (color), yellow 5, yellow 6, red 40, BHA (used as a preservative), blue 1, dl-methionine
OK the bone meal may contain lead, BHA causes cancer,dyes cause seizures. Not to mention all the other absolute junk in this food.
Orijen
Boneless chicken,* chicken meal, chicken liver,* whole herring,* boneless turkey,* turkey meal, turkey liver,* whole eggs,* boneless walleye,* whole salmon,* chicken heart,* chicken cartilage,* herring meal, salmon meal, chicken liver oil, red lentils, green peas, green lentils, sun-cured alfalfa, yams,* chickpeas, pumpkin,* butternut squash,* spinach greens,* carrots,* Red Delicious apples,* Bartlett pears,* cranberries,* blueberries,* kelp, licorice root, angelica root, fenugreek, marigold flowers, sweet fennel, peppermint leaf, chamomile, dandelion, summer savory, rosemary, Enterococcus faecium + vitamins and minerals
Real food real ingredients