Unless you want to start learning about every single chemical they put in food, it's a good general rule that lower list of ingredients is better. Sugar and salt lower down on the ingredients list is also better. For processed meats, usually it should have the percentage of the product that is actually meat too, so if you're buying a pack of sausage &amp; it says pork (30%) then you might want to wonder what the hell makes up the rest.

Oh, edit to add: you should eat whole grains over white grains where you can, because a lot of the good stuff in grains is in the skin of the grain. There are probably some other things where the skin has a lot of nutrients but I think grains (wheat, rice, barley, etc) are the most clear example.