Before you buy new food, go on the websites for different food companies - lots of times you can get free samples. If there's no link for free samples email the company and ask for one. When we first got Roscoe he was VERY picky, so that's what I did instead of buying many different kinds that he would not eat. We settled on Biljac (you can get it at petsmart, and they will send you a large free sample for going on their website). We went through many free samples before finding one he's eat.

I also want to mention that, although you want a good brand of food, it won't do any good if they won't eat it. Some people have told me that Biljac is not as good as some other brands, but Roscoe has been doing wonderfully on it. The vet said that he is MUCH healthier than when we first adopted him. It's really up to the individual dog, I know people that fed Purina to their dog and she was a very healthy dog until the age of 17. Each dog is different, that's why there are so many different kinds of food