In a few rooms of the house, someone painstakingly tore pieces of wallpaper and glued them to the walls. One of the first things I did (after my girls discovered wallpaper was removable, hence it's short lifespan at our house), was tediously tear it down piece by piece. Most of it came off without much trouble but a few spots were a bit tricky. Here's a simple recipe to help the stubborn pieces slough off.
Ingredients: 1 cup white vinegar 1 cup water
Mix thoroughly and pour into a spray bottle. Spray generously (but do not saturate) wall paper, waiting a few minutes before peeling or rolling off. If the glue or paper is particularly stubborn, score the wall paper lightly with sandpaper and respray.
...or roll and peel.
Soon enough your walls will be ready for redecoration!