Dust the drywall with a microfiber cloth or dry duster
Vacuum the surface with a soft brush attachment
Mix warm water with a small amount of mild dish soap
Dampen a soft sponge or cloth with the solution
Wipe the drywall gently in small sections
Avoid soaking the drywall
Use a clean damp cloth to remove soap residue
Dry the surface immediately with a soft towel
Spot-clean stains with a baking soda paste or gentle cleaner
Test any cleaner on a small hidden area first
Repair damaged or crumbling drywall before cleaning
Repaint if stains or marks do not come off