How do you get old wallpaper off drywall so you can repaint?

I just pulled down some decowallboard from my bathroom walls that the previous owner had put up. There is the remnance of some hideous old wallpaper that they had stripped off the wall but didn't get it completely off. I need to try and get as much of it off so I can paint the drywall. Can anyone tell me what the best procedure is for what I want to do?