Is canned food or dry food better to start kittens with - and at what age?

Canned is better to start a kitten on; it isn't as hard for them to eat.

Mushed up wet food, or wet food that is throughly mixed with a little water or kitten milk is the best type of food for weaning and young kittens. It is easy for them to eat and digest. It is advisable not to try dry food as, even softened with water, kittens may still not be able to eat it. Dry food is incredibly hard and brittle, and is often full of corn, wheat, and other grains and cereals which provide nothing in the way of nutrition to a kitten or an adult cat. These ingredients are often hard to digest; cats have evolved to derive all needed nutrients from meat, not plants.

Kittens usually begin the weaning process around 4-6 weeks of age. They begin by taking an interest, or picking at their mother's solid food. At this age they will still be suckling and getting nutrients from their mother, but putting a tiny bit of wet food down every few hours will entice them to eat. You could see if they will lick food off your fingertip or off their own paws. This first stage can take several days.

As the kittens get older and bigger, you can slowly decrease the amount of water or kitten milk you use in the food, and leave slightly larger chunks for them to chew.

Be sure to feed them from a plate and not a bowl, as it is easier for the kittens to pick up the food.