Avoid correcting your child or you might discourage him. A good way to help your child learn the "right" way to say something is to affirm what he says, using the correct pronunciation, sentence structure, or grammar. For example, if your child says, "The mail comed," you might say, "You're right. The mail came. Let's see if we got a letter from Grandma."
Excerpt from "Learning Two Languages." Reprinted with permission from PBS Parents.