As with most big jobs, the prep is the most important part. Stripping old wallpaper is a dirty, messy — and wet — job and the right prep steps will make a huge difference. Remove switch plates, vent covers and cover the floor completely with a drop cloth. Don't forget to include baseboards. Bring the drop cloth up and over the baseboards and secure with tape to keep the water from warping them as you work.
Grab that little corner that's already coming off the wall and let 'er rip! Rip off as much of the wallpaper as you can to expose the bottom layer of the paper and glue. The more you rip now, the less scraping and cleaning you'll have to do later.
Scoring means poking little holes in the paper so that your solvent can get underneath to do its job. Scoring is even more important to get under vinyl coated wallpaper or professionally installed wallpaper that won't come off the wall with a simple rip. There's really no need to buy a professional scorer; a fork will do the job just as well. Just make sure you use a fork you won't mind throwing out later. Run that fork all over the surface of the wallpaper, shredding as you can to make as many nooks as you can to get the solvent on.
Use a sharp edge to cut any wallpaper away from base boards, moldings and chair rails in case there's any paper stuck underneath that might make removal tougher.
Skip the chemical solvents and mix one of these household items with boiling hot water instead. DIY-ers swear by different mixtures, so test each one on a section of wall and see which works best for your job: fabric softener, corn starch or white vinegar.
Again, make sure your solution is really warm. Keep a tea kettle on the stove and add hot water occasionally to keep your mixture nice and hot.
You can use either a spray bottle or sponge to soak the wallpaper, but be sure to only soak a section at a time because once that wet paper dries again, it's going to be even harder to scrape off. Only wet sections that you can scrape off in about 15 minutes.
For really stuck-on wallpaper that won't budge with solvents, you're going to need to bring in the big guns — a steamer. The industrial ones are heavy and loud and messy and most household jobs can be tackled with a little handheld steamer you can pick up at a hardware store for less than $100. That's probably the best place to start. The steamer essentially just replaces the soaking part of the process.
One tip: Steamers tend to drip and spritz water all over the place, so before you start steaming, make sure you've got plenty of old towels around to sop up the spills.
OK, so the scraping is totally the worst part. And besides using the right solvent to dissolve the glue, the only thing that gets this job done is good old-fashioned elbow grease. One way to keep yourself from having to kneel in soggy, dirty wallpaper shrapnel is to start at the bottom of the wall and work up. As you get higher, place a big trash barrel under your scraper, so as much wallpaper falls directly in as possible, saving you a bit of cleanup.
Once you've got the wallpaper off the wall, clean off any bits of glue left on the wall by using a mixture of water and laundry detergent. That should get the surface clean and ready for painting, or whatever you plan to replace the wallpaper with.
Good luck getting rid of Granny's old wallpaper. Here's a great video tutorial to help you along.