Depends on what adhesive is used. Old style adhesives use mineral spirits. The new ones use alcohol/water (acetone is an alcohol), silicone, 2 part systems and there are plenty I have never run into.

You can start with mineral spirits and move to soap and water and finally add acetone to the soapy water or you can do what I do and buy some 3M decal remover.

There are probably some newer systems that cannot be dissolved. These will not be "sticky". You will have to remove them mechanically.