Depending on the type of paint and wallpaper, it can be a relatively simple job, or a very long one.
Steps
Step 1. First, identify the type of paint used
Apply a pinch of solvent to a paper towel, and rub into the paint in question. If the paint comes off on the handkerchief with the enamel, it is latex paint, otherwise it is alkyd (oil). The latex one is water soluble and will be easier to handle, while the other is more "sticky" and it may take a few more attempts to remove the paper from the wall.
Step 2. At any hardware store or department store, buy a "paper tiger"
It is a small tool with several moving wheels and teeth to cut paper without damaging the underlying surface.
Step 3. Engrave the card you are removing
Pass the tool over the area several times, to pierce the paper as much as possible. Just push through the paper, trying not to damage the surface underneath.
Step 4. Remove any covers from sockets and switches, if any
If there are sockets or switches in the work area, be sure to turn off the power.
Step 5. Add a cup of fabric softener to half a bucket of warm water
Dip a sponge into the mixture and squeeze it to keep from dripping.
Step 6. Sprinkle the wallpaper with the water / fabric softener mixture
Let it soak for 10-15 minutes.
Step 7. Try to grab a corner of the card and pull
The paper may come off the wall; otherwise, sprinkle the area again, wait and try again. You may need to do this a couple of times, in case the paper and paint have been there for a long time.
Step 8. When the paper begins to peel off, use a plastic putty knife (or nylon spatula) to remove all the paper from the wall
Step 9. Once the paper is removed, apply the softening mixture to the paper again
Proceed as in steps 7 and 8 until all paper is removed. You will not have to engrave the paper, as it is unpainted and has no vinyl or similar coatings.
Step 10. When the area is free again, wash with detergent to remove glue and fabric softener residues
Rinse one last time with clean water.
Step 11. Let it dry (best at night)
Sand the area and repair any damaged parts with putty or sawdust.
Step 12. If you have had to make repairs, give it a final sandblast
Cover the surface with a coat of primer (if you intend to paint) or wallpaper.
