There's a duality of characters in the film. John is also Scottie. Judy the shopgirl takes on another identity. She'll be a lost love. In movies, mirrors are great for reflecting duality.
Before Vertigo airs, there's a special with its star, Kim Novak. TCM host Robert Osborne interviewed her during this year's TCM Film Festival in Hollywood. His interview airs 8p Eastern/5p Pacific followed by the brilliant Hitchcock film.
During the movie, just for grins if you watch it with friends, you could try to Vertigo Drinking Game that I came up with about a year ago. Do a shot of something whenever you see a human figure fall in Vertigo. Be ready as soon as the movie starts.