If you have an uneven ceiling with ridges and bumps, simply painting over it will not fix the problem. Since painting a ceiling can be hard on your arms and shoulders, don't just start painting and hope for the best. Instead, follow a few simple techniques to even out your ceiling, then apply new paint to a flat, prepared surface.
Things You'll Need
Lightweight joint compound
Cover the floor of your room with painting drop cloths.
Stand on a stepladder so you can reach the ceiling. Sand or scrape any raised areas, dried paint drips or bumps off your ceiling using sandpaper or a razor knife.
Apply a thin layer of lightweight joint compound to the ceiling using a taping knife. Allow the compound to dry overnight.
Put on a dust mask. Sand any rough edges or raised spots.
Repeat Steps 2 and 3 one or two more times until you are satisfied with the smoothness of the ceiling.
Tape the walls at the edges of the ceiling using painter's tape. Use a paintbrush to paint around the edges.
Pour ceiling paint into a tray. Use a roller to apply it to the ceiling. Let dry for 24 hours, then apply a second coat if desired.
Using several layers of thin drywall compound will give a smoother finish than one layer of a thick compound.
Use caution when standing on a ladder.