Before starting this chore, do make sure you protect your floor and skirting boards as everything is likely to get very damp and sticky.
The first step is to tear off the facing of the old wallpaper. If you can, start at the top or around a switch, where it is likely that there is already a little bit of loose wallpaper and then pull, exerting a slow, steady pressure. This stage, requires no water, unless you find that the wallpaper has been on the wall for a very long time and that it is not possible to remove the facing from the backing. In which case, you will need to score the paper, with vertical and horizontal cuts.
The next stage is to soak the backing paper with hot water by using a sponge or a floor mop. Allow the water to soak into the paper and soften the glue behind, for at least 15 minutes. If you are prising old paper off of a plaster board wall, then you must be careful not to soak the wall too much. Plaster walls can take more soaking.
Next, using a metal scraper, gently scrape the soaked backing paper and the glue off the walls. Make sure you don’t damage the wall underneath and it is advisable to use a scraper with rounded corners. Once this is done, check that all the glue has been removed. Wash plaster walls with warm, soapy water. If they still feel sticky, you will need to scrape off any paste residue and you may have to resort to chemicals to do this.
Once all traces of wallpaper and paste have been removed, you need to sand the wall, fill any holes and sand again, before your wall is ready for new paint or new wallpaper.