Clear the room of as much furniture as possible. Remove window coverings, wall decor, lights and ceiling fans. This will be a messy job.
Protect the floor with drop cloths and drape plastic sheeting over remaining furniture, cabinets and fixtures.
Assess the damage. Fill small holes, such as from plant hooks, with lightweight spackle. Dab it into the hole with your finger, leaving a bumpy surface to match the popcorn ceiling. Fill narrow cracks with caulking, smoothing it with a damp rag so it blends in with the popcorn texture while filling the crack.
Remove loose or sagging popcorn texture with a paint scraper. Patch the underlying damage with fiberglass drywall tape and spackle if necessary. Let spackle dry for about eight hours.
Spray aerosol popcorn texture from a spray can for repairs larger than 2 inches in diameter. Spray a light coat initially, blending it into the surrounding area. If it looks too thin, spray another coat after about 30 minutes.
Prime the ceiling with fast-drying oil- or shellac-based primer if the ceiling has never before been painted, or if it is stained with nicotine or water-stains. If the ceiling is painted and only stained in a small area, use stain-blocking primer from a spray can to prime only that area. Allow the primer to dry according to label directions.
Roll the ceiling using a foam roller specifically designed for rolling over popcorn ceilings. Regular rollers will quickly become clogged and matted with pieces of texture. Apply two coats of flat ceiling paint to minimize the appearance of uneven repairs.