They sell wallpaper remover. Can't remember the brand but the type I used was sort of yellowish brown in color. Almost like piss colored but a little darker. It softens up all that old glue. Next thing you need is a wallpaper perforator. It is a palm held thing you can pick up for a couple bucks. It has a few wheels on it with little teeth and you roll it around and it perforates the wallpaper with a bunch of tiny dots. Makes it much easier to take off.
Now, if you want to get serious with it, go to your local hardware rental place and rent a wallpaper steamer. Get the job done in half the time but it will cost a few bucks for the rental. Probably something like $30 per day but if it's a large area, it's worth it.
Hope I helped
