For newer Disney releases, the stickers usually aren't heavy on the glue. I apply a bit of heat from a hair dryer on low from a good distance for about 10 seconds (if you look closely you can actually see the sticker start to release on it's own once it's heated), then use a small bit of scotch tape to lift a corner without risking scratching to the lenti/slip. Should peel right off at that point.
Works for other studios too but Disney is probably the most consistently easy for me.