basically when selecting a food, you want to look at the first 4 ingredients. ideally you want those 4 to be some sort of meat product with the first ingredient being "chicken" or whatnot. you absolutely want to avoid foods that have corn or corn meal in the those first 4 ingredients.

a good brand, if you can find it is "chicken soup for the cat lover's soul". its made with fresh chicken and has an excellent ingredient list. plus its relatively cheap. usually its only found at feed stores, but if you check the website they have a store locater feature.

i recently switched my cats off eukanuba to a different brand, whose name i can't remember atm. i got it from petsmart and after looking around it had the best ingredients.