Read a favorite book together with your child. Point out that each sentence starts with an upper-case or capital letter. Also find an example of those same letters in lower-case.
Reading aloud is always one of the best ways to help your child build oral language skills and start down the path to learning to read. Learning that the letters of the alphabet have two versions—upper- and lower-case—will help your child recognize different letters. He also will begin to see the print pattern of sentences—that they always start with a capital letter and end with a period.
 
Oral Language, Print Awareness and Alphabet Knowledge