Check a day's worth of programming across the channels. Let the networks know. Try This Turn down the sound of your family's favorite sitcom and take on the roles of the characters as you take turns reading dialogue. See who spots the mistakes first. When appropriate, point these new words out - children are most likely to remember a new word if they hear it in context and see it in writing at the same time.
Closed captions can be particularly useful if there's a reason to be quiet in the house.
If not, join them and help them share the story through the captions.