Warm the car up, best in a warm garage, if cold it'll just tear and will leave the glue behind, a hairdryer will be useful.
Pick at the edge to get some up then pull it off away from it self, not over itself, as in your pulling it towards you not tearing it away.
Some kind of thinners will get the glue off, use only a tiny amount in small patches as all you do is smear the glue around, it's a proper pain and window tinting co's charge by the hour to get it off
Don't use a stanley to scrape the glue off, you'll scratch the glass