To remove wallpaper glue residue from walls, start by mixing warm water with a few drops of dish soap. Apply the solution to the residue using a sponge or cloth, then let it sit for a few minutes. Use a scraper or putty knife to gently scrape off the residue, being careful not to damage the wall. If the residue is stubborn, you may need to use a commercial wallpaper glue remover or sandpaper. After removing the residue, rinse the wall with clean water and let it dry completely before painting or applying new wallpaper.