Remove all items from the room you are painting and cover the entire floor and all surfaces with drop cloths. Tape plastic over the windows, window sills and doors to protect them from splatters. In addition, remove all light fixture globes from the ceiling.
Open a can of stain-sealing primer and pour it into a paint tray. Insert a long-handled paint roller into the primer and push the roller along the ceiling in long, even strokes to apply it. Work in small 4- to 8-foot long strips along the length of the room so you don't miss any spots. Allow the primer to dry and apply a second coat.
Allow the ceiling to dry completely for 24 hours to ensure the primer is no longer sticky.
Pour a latex, water-based paint into a clean paint tray. Flat paint is generally best for ceilings.
Insert a clean paint roller into the paint until it is saturated. Apply the paint to the textured ceiling in the same way you applied the primer, using long, even strokes. Allow the ceiling paint to dry and apply a second coat.
Pick up the paint can and place a ladder along one side of the room. Climb up onto the ladder and use a 2 1/2-inch angled paintbrush to paint all the way around the edge of the ceiling where it meets the wall.
Remove all the plastic and the drop cloths from the room and discard them before returning the room's furniture. Reattach light fixtures to the ceiling once it is dry.