The hot water will wet the wallpaper and it will be possible for you to strip off the wet wallpaper easily. In some cases a mixture of hot water and vinegar is applied on the wall paper. This mixture is usually sprayed over the old wallpapers.
In some cases, a wallpaper remover is used in place of the water-vinegar mixture. You need to follow a specific pattern while removing the old wallpapers. For example you can strip the wallpaper from left to right, from right to left, from one corner to the other, from top to bottom or from bottom to top.