Recommended Surface Prep
The surface to be painted should be dry and free of any dirt, chalk, grease, oil, loose or peeling paint or other foreign contaminants. Remove dirt, grease, or oil from wallboard with a detergent solution, rinse thoroughly, and allow the surface to completely dry. Repair/Caulk all cracks and fill all small holes and other surface imperfections with putty or spackling compound and then sand to smooth finish followed by dusting. Old glossy enamel finishes should be sanded to a dull finish, dusted, and then primed with the appropriate primer. Remove sanding dust by wiping with a damp cloth or sponge.
Always prime new or bare drywall with the appropriate primer to ensure good enamel hold out of the finish coats. Latex primers are recommended for normal wallboard surfaces, because oil-based primers have tendencies to raise the grain of the paper.