Place a drop cloth on the floor beneath the area where you will be working. Tape around corners where the ceiling and other walls meet the affected wall to keep splatters or spills from getting on them.
Fill holes and scratches in the wall with drywall compound. Use a trowel to spread the compound over the damaged area and force it in. Smooth it out with a slight raise as the compound will shrink a little as it dries. Let it dry for several hours.
Sand the surface of the repair to smooth it even with the wall.
Repaint the wall if holes and scratches were the only problems or if you don't like the existing paint color. Use a paint roller to cover the bulk of the area, running it up and down in long even strokes. Paint along the edges with a paintbrush to keep splatter and spills to a minimum.
Cover the wall with a texture if the wall has other issues, such as a slant or crooked angle. The texture will break up the lines and make it less obvious. Scrape drywall mud onto the surface of the wall with the trowel in swirl or crisscross patterns. You can also fill a paint sprayer with a thinned drywall texture compound and spray it on the wall. For a speckled look, leave it as it falls or knock the peaks down with a trowel for a plaster effect.
Paint over the texture after letting it dry for a day. Use a paintbrush as a roller won't work well on the bumpy surface.