How can one know that this is not a dream? If it's in the movie, Nolan will hand you a small, non-resistive cyclone gyroscope without saying a word. As long as you throw that thing on the table and wait patiently for an hour or two, you will know the answer, provided you have enough patience, of course.

If it's on TV, it's simpler. You don't need patience and perseverance, just a little courage. Yes, it's the bridge section that has been rotten by countless bad directors. Take a decisive breath out of your arm, or slap it hard on your innocent little face. You know where the road is...