maddenbowler has it 100 percent!!! I do motor vehicle inspections and tint is illegal on front windows. Peel the tint off, leaving the adhesive behind. Spray the adhesive with windex or glass cleaner. Now scrape the adhesive off in strips with a BRAND NEW RAZOR BLADE
. Here's the point: you don't want to dissolve the adhesive. If you do, it just ends up smearing around, making a bigger mess. The windex just acts as a lubricant that prevent the adhesive from resticking. That being said, if the glass cleaner has a lot of ammonia in it, it will soften the adhesive. The reason for the new razor blade is obvious: a used one could scratch the glass.
Now, if you have to remove it from a defroster grid window, good luck!