Scrape any bumps or ridges from the wall with a wide putty knife. Tap any nails that may be protruding from the drywall into the wall with a hammer or pull the nails with a pry bar. Don’t worry about damaging the wall at this point. Remove any wallpaper or wallpaper glue that may be on the wall, as well.
Sand any remaining rough edges lightly with fine-grit sandpaper. Wipe dust from the wall with a tack cloth.
Apply a small amount of Spackle to cracks in the wall. Work the Spackle back and forth across the imperfection to work the Spackle into the opening. Place another thin layer over the top of the first layer and feather the edges on the wall. Larger cracks may take extra layers of Spackle to fix. Follow the manufacturer's recommendations for drying time.
Pull any loose drywall from holes with your fingers. Sand edges with fine-grit sandpaper to smooth them. Wipe off grit from sanding with a tack cloth.
Measure a piece of drywall repair mesh for larger openings that you are repairing. Choose a patch large enough to cover the hole plus 1 inch on all sides. Cut a patch to fit over smaller holes, allowing 1 inch extra overlap onto the wall.
Dip a putty knife into a container of Spackle. Spread a thin layer of Spackle around the opening to the hole in the drywall, as well as in the hole.
Set the mesh into the Spackle and spread it out so it covers the hole. Apply another thin coat of Spackle over the mesh to embed it in the compound. Feather the edges of the Spackle onto the wall to blend it in with the existing wall surface. Depending on the size of the hole, it may take three or more thin layers of Spackle to repair it. Allow the Spackle to dry according to package directions.
Sand the repaired surface smooth with fine-grit-sandpaper. Remove any grit with a tack cloth.
Apply a coat of primer to the repaired areas of the wall. Allow it to dry.
Apply two coats of interior paint, allowing the first coat to dry thoroughly before proceeding with the second. For best results, paint the entire wall where you did the repairs. Avoid glossy paints as they are more likely to show repaired areas than flat paints.