It depends on what the label is on. I typically use white vinegar or isopropyl alcohol. That quickly dissolves the glue as well as the paper. However, if your label is on a non-fast surface such as porcelain, or particularly on a porous surface, such as fine woods, etc. then I use a small dab of camphor oil � first testing the area. The smallest residues can be initially loosened by using a rubber. However, you must be careful not to rub too deep into the finish.
I wish you the best of luck
Fr. Bill