The type of wallpaper in question is an important factor in its removal. Some wallpapers have a vinyl coating that makes them moisture-resistant. This resilience is a good thing if you want the paper to remain on the wall, but it complicates removal, and the vinyl may need to be sanded off before the paper can be removed. Some wallpapers are made with removal in mind. These are call strippable or peelable wallpaper, and they're designed to peel off the wall like a big sticker.
Make a mixture of a 1:2 ratio of fabric softener and hot water, or add a cup of vinegar to approximately 2 gallons of water and spray the liquid on the wallpaper. The liquid should loosen the wallpaper glue, making it easier to peel off.
Perforate the vinyl with a scoring tool, or sand vinyl coatings off wallpaper, prior to applying a loosening agent.