Duct tape some plastic along the base board to catch any liquid mess (be careful, as the plastic can get slippery as it collects the gunk)
Score the paper. They make a Paper Tiger specifically for this, or you can lightly drag the toothed edge of a handsaw across the surface.
Purchase some of the wallpaper remover available at local paint store, or big box store.
We used to apply it with a Hudson sprayer, but a large (4" paint brush will work.
Hopefully, the paper hanger had the walls sealed with an oil base primer before installing the paper. If so, take a 4 or 6" taping blade and scrape the dampened paper off the wall.
Again, if the surface underneath the paper was sealed beforehand, be sure to take a damp sponge and thoroughly rinse with clear water to remove any residual wall paper paste as the water in latex paints will re-wet residual glue/paste, and can cause adhesion problems or alligatoring.
If you want to take the extra step: when the wall is thoroughly dry, reprime it with something like Gardz, which will ensure a tight surface. You don't have to be as careful to get all the paste off if you take this step.
Is the paper face smooth or surfaced (flocked, etc.)? I ask because if the paper is tight to the wall you can prime it with a quick-dry oil base primer and then texture or paint over that substrate. I would avoid latex primers because of the chance of the water penetrating the paper, re-wetting the glue, and causing bubbling, decreased adhesion, etc. If the original surface wasn't primed before papering then this might be your best option.