Check the protective film for adhesiveness. Try lifting an inconspicuous corner of the film. Many newer protective films are made of thin, self-clinging vinyl, similar to the protective covers found on new cell phone, television and computer screens. Try lifting the corner with your fingernail or lightly probe the corner with the scraper.
Pull the corner of the protective covering downward at an angle toward the lower, opposite corner with a gentle, smooth motion. A reusable covering should peel off the window glass relatively easily.
Spray the protective film with ammonia or the alcohol solution to soften it if the film does not come off the window easily. Mix 1 tablespoon liquid dish detergent, 2 tablespoons of baking soda and 1 pint each of warm water and isopropyl alcohol and pour into the spray bottle, or just use full-strength ammonia in the spray bottle. Be careful not to get the ammonia or alcohol mixture on the window frame or the vehicle's chrome surfaces.
Wipe up any runoff with a cloth or paper towel. Cover residential glass panes with plastic wrap or newspapers. Use black plastic garbage bags to cover vehicle windows. Press the plastic or newspapers to the pane with your hands.
Let the ammonia or alcohol mixture soak into the window film for an hour or more, then lift the plastic or newspaper and use your fingernail or the scraper to lift a corner of the film. If the film is not quite soft enough, spray the protective film again, replace the plastic or newspaper and wait at least another hour.
Peel away as much of the softened film as possible with your fingers. Use the plastic scraper to remove any remaining bits of protective film. Use window cleaner or ammonia to remove any leftover adhesive and use the squeegee to remove the excess. Finish drying the window with the soft cloth or paper towel.