Next time you've got to make sure that the silver layer is attached to the hard clear layer as you peel it off.
There's no easy way to get the glue/silver stuff off once it becomes separated from the other layer. As the people above said; all you can do is spend ages with a razor, q tip and rubbing alcohol but there's a good chance you'll end up with some screen lines.
Best thing is to pick up some cheap grey boys/pockets to practice on.