Go to the hardware store and buy a can of Xylol (probably spelled wrong, but close..) and wipe the window with that stuff on a rag. Let it sit for a few minutes, then come back out with a razor blade and scrape til the tint itself is off. Wipe the window down again with the Xylol and then use a new razor blade to scrape that sticky crap off (which will be more like the consistency of a booger when the Xylol is applied.)
Another method (can't recall it's name,) is to mix up the solution of water/amonia, and apply it to the window, then cut up a black garbage bag, and stick it up against the window, then let it sit out in the sun a few hours. When you come back and peel the garbage bag off the window, it'll take the tint with it.
On the back glass with the defroster use a steamer to save the lines...it will also help to start one corner of each window and use the steamer or adheasive remover behind there.
Also, I had VanHorn (a window tint shop in town) tell me to make a real sudsy solution of soap and water and lather the window and then stick plastic grocery bags to it... let it sit and dry out in the sun and then pull the bags away and the tint will come with it. This is a very good method because it saves the defrost lines and keeps you from using a razor blade too much. And its cheap!