Plan on working for about two hours.

Cut a garbage bag along the sides so that you have one
large sheet of plastic, and place it on the back deck of the
windows to catch any film and glue.
Remove Window Tint from Rear Window
Use a single edge razor blade to peel the plastic film off
at  the top corner of the  window , where there are no
defroster lines. You only need to peel back very little so
you fingers can hold onto the film.  When you can hold
the peeled part of the window film, pull it very slowly
through out the whole window.  The film should peel off in
one piece most of the time.  If you need to use the single
edge razor blade  to help start the film removal again, be
very careful not to hit the defroster lines.  If you do hit the
line(s) that line(s) won’t work again.

After all the film is removal from the window the only thing
left is the glue. Spray a mixture of soapy water (couple of
drops of dish soap and water) or window cleaner on the
window.
While the soapy water is still on the window.  Scrub the  
adhesive off with fine (000)steel wool . This will take time,
so be patient.  Keep spraying the window with the mixture
until all the adhesive remove.   

Remove Window Tint from Home & Side Automobile
Windows

Catch the top corner of the film with a single edge razor
blade.

Continue peeling the film off with a single edge razor
blade or with your hands. You may have to take it off in
several pieces.
After all the film is removal from the window the only thing
left is the glue. Spray a mixture of soapy water (couple of
drops of dish soap and water)  or  window cleaner on the
window . While the soapy water is still on the windows,
then slide the razor over the surface of the window to
remove the remaining residue.  You might need several
razer blades.