Let them in on some of the illusions. Tell them that white glue poses as milk in cereal commercials. TV teaches that some people are more important than others. Point out the predominance of white male perspectives compared to those of women and minorities. Keep track of what people are shown as victims or losers.
TV keeps doing the same thing over and over.
Make a game out of counting the camera shots in a car chase scene. Check out the music changes during an action climax. Add up how many shows a week are actually the same story with different actors. Somebody's always trying to make money with television. Count up the number of commercials in a half-hour and time them.