To paint an interior wall, remove all items from the wall and place painter's tape around any part of the wall you don't want to get painted. Once you complete the prep work, coat the wall with primer before actually painting the wall.
When preparing an interior room for painting, it's important to remove all items from the room and cover the floor so as not to get paint on them. Clean the wall to make the application of the primer and paint much easier. If there are any cracks or holes in the wall, patch them and sand the surface until it is smooth.
After the room and the walls are prepared for painting, the first step is to apply a light coat of primer. Add a small amount of primer to the paint tray until the bottom portion is covered, and then apply the primer to one section of the wall at a time.
Once the primer dries, apply the paint. It is common to paint the wall in a large "W" until it is covered. An important thing to remember is that you should use different brushes for different parts of the interior wall. A roller brush is useful for painting large portions of the wall, but edges should be painted with a straight edge and angled paintbrush.