100% the best way is ammonia. if you have tint you want to clean, be sure you do NOT use a cleaner with ammonia in it, it will peel your tint right off. works like a charm.
Get a can of Oops from Wal-Mart. I've used it on several cars. No razor blade required. It will just eat right though the glue and you can do every window in under half an hour. Don't spill it on anything else though or life will suck.
All use a razor blade, be sure to buy a very good holder/handle for the blade. It makes all the differance. I got a long one with a screwdriver type handle and it really helps the job go easier and faster.