On the way home from the hospital! When you read aloud to a baby, he or she is growing used to the rhythmic sound of your voice and associating it with a peaceful and secure time. In other words, your baby is learning to associate words, language and reading with pleasure.
When your child is an infant, what you read is not so important -- it's the act of reading that matters. Of course, oral stories, songs, rhymes, lullabies and chants are all part of the early reading process. The child will grow used to them, will develop favourites and will start repeating them.
When the child's sight and hearing have developed (at about 10 months), using actual books becomes more important. Picture books with simple, bold illustrations and bright, solid colours are most effective at this stage. Use the book to point our familiar objects and repeat simple words (such as mommy or daddy). And use it as an object of play. Leave one or two books in the playpen or crib.