Like human babies, puppies begin their lives receiving nourishment from their mother's milk. At some point, of course, they need to be weaned from the milk to regular dog food, either because they're adopted out to a different family, their mother's milk dries up or they get too big to be able to survive on milk alone. Weaning typically starts at about three-and-a-half weeks of age, with the process usually completed by the time puppies are seven to eight weeks old.
Determine the brand of dog food you'll use. It's best to use the same brand of dog food (e.g., Iams, Purina, Science Diet) that the mother eats, as the puppies' tiny digestive tracts will be used to that particular mixture of ingredients. Choose the puppy version of that brand, which is formulated especially for growing puppies.2
Since your puppies are used to eating nothing but liquid at this point, you don't want to go directly to dry food, which can be difficult for them to eat. Instead, prepare a puppy mush from the dry puppy food to help ease them from milk to regular food. To do this, put two cups of dry puppy food and 12-1/2 oz. of puppy milk replacer, which can be found in pet supply stores, into a blender. Fill the rest of the blender with hot water. Blend the puppy mush. Keep blending until the mixture resembles infant cereal, or creamy oatmeal. This should be enough to cover one meal for six to eight puppies.3
Introduce the puppy mush into the puppy's diet. Dish out three to four meals of the puppy mixture per day.4
Gradually decrease the liquid until your puppies are eating dry food. Each day, put less milk and water into the mixture. By the time your puppies are seven weeks old, they should be completely weaned from milk to regular food.