I have a laminated stoplight for each student in my class. On Mondays we introduce our new story in reading and the vocabulary words. Each person writes the words on the light that's appropriate for them: words they know, words they think they know, and words they don't. We use this as a learning opportunity to share with others, and then look up the words in the dictionary that we couldn't define as a group. This is a wonderful cooperative activity and ensures that everyone is familiar with the new words we'll read in our new story.