Sheen is almost as important as color when it comes to wall paint, and you have at least five sheen choices, ranging from full gloss to semigloss, satin, eggshell and flat. The glossiness of a paint is determined by the ratio of binder to pigment; the more binder, the glossier the paint. Eggshell isn't very glossy, but it is glossy enough to create adhesion problems when you repaint it. Improving adhesion is a three-step process involving washing, sanding and priming the wall. The process ensures that any paint with any sheen, including dead-flat, will adhere well.
Move furniture out of the room and cover the floor with plastic dropcloths.
Mix a solution of 3 ounces trisodium phosphate per gallon of warm water in a bucket and use a sponge or rag to wash the walls with the solution. TSP is a powerful detergent that lightly etches the finish and deglosses it.
Let the wall dry completely, then sand it lightly with a pole sander and 150-grit sandpaper. The abrasive action of the sandpaper deglosses the finish even more. Wipe the wall with a dry cloth when you're done sanding.
Prime the wall with polyvinyl acetate primer, applying it with a brush or roller. PVA primer, also known as drywall primer, contains the same adhesive that's in carpenter's glue. It sticks well to an eggshell surface, and new paint bonds well to it.
Brush or roll one coat of flat paint, let it dry, then apply a second coat.