Prepare the wall:
Clean the surface thoroughly to remove dust, greases and previous paint.
Inspect the surface:
Find the dents, holes, and imperfections that need to be fixed. Use wall putty or plaster to fill them up and sand the wall to get a smooth surface.
Cover all the open surfaces that do not need to be painted including switchboards.
Apply the primer:
Apply one or two coats depending on the paint type you are using.