To start off with you will need the following items:
Brand new razor blades (the kind that fit into widgets or scrappers)
Fine steel wool
Two large black plastic trash bags
Window cleaner with high ammonia I use non-ammonia Eagle One glass Cleaner-
We will start buy parking the vehicle in the sun with the rear of the vehicle facing directly towards the sun. Using one of the razor blades; cut along the right edge seam of the bag. Cut the left seam in the same way. Now the the trash bag can cover twice the surface area for larger windows. Do the same to the second trash bag. Now you will spray a large amount of the window cleaner onto the inside of the rear window. Now quickly adhere the bag to the rear window. It will stick to the glass with the moisture of the window cleaner. Make sure the entire glass surface of the rear window is covered. This process is known as sweating the film. You will need to apply more window cleaner every 20 minutes or so depending on the outside temperature, Do not allow the window cleaner to evaporate. You will allow this to sweat for 2 hours in the direct sun light.

While this is taking place you can work the side windows. Using a new razor blade start at the top of the window edge and peel the film off. If the film is newer, chances are it will come off in one piece, if older it may come off in several pieces. Once the film has been completely removed from the glass you will remove the glue film that is left behind. Soak the entire window with the window cleaner. Start at the top and scrape the glue towards the bottom. The more consistant you are with your removal strokes the easier it will be. Make sure to keep the glue wet with window cleaner at all times. When All the glue is removed you may clean the glass with a clean paper towel. This part of the process will take approximately 25 minutes per window.

When all side windows are complete you may remove the black trash bags. In the middle of the window cut a seam in the film. You will be able to peel the enitre film off the glass quite easily and effortlessly. The glue in most cases will come off with the film however do not panic if it does not. Simply use the steel wool in the same fashion you used the razor blades on the side glass. We use steel wool so you do not damage the orange rear window defrosting filaments.

SLD's way:
Grab 5 new razor blades, Heat gun, Eagle One Foam Glass cleaner, Prepsolvant, cotton towels, Microfiber towels

HOkay so...... see if the tint peels off the window andif it rips and comes off in pieces then use the heat gun , that usually works for me, once you get the film off use foam glass cleaner and prep solvant on the defrost windows.. bout sums it up..
takes me about 30 mins on a easy car and 1.5 hours on a hard car... im sure the boys at Tintmaster have has some tough jobs...