Match life stage and species, read labels, and change diets gradually over a week.

Pick food labeled for your pet’s species and life stage: puppy/kitten, adult, or senior. Breed size and activity level also matter.
Look for a clear protein source and AAFCO or equivalent complete-and-balanced statement. Avoid sudden brand hopping.
Transition over 5–7 days by mixing increasing amounts of the new food. Watch stool quality and energy during the switch.