Remove the door from its hinges. Use a screw driver to remove any hardware from the door, including door knobs, door knockers and hinge panels. Place the hardware off to the side, and tape the screws to the hardware, so you do not lose them.
Take the door to a place in your house or outside your house where you aren’t worried about getting paint on the floor, but where you can lean the door against a wall. Place the door on the floor or ground on a tarp, and lean the door against a wall.
Wipe down the door with a rag. If the door has visible dirt, use a damp rag or a mild detergent mixed with water.
Sand the surface of the door with a fine sandpaper. Doing so will rough up the surface of the door so it will hold paint without chipping.
Paint the door with a primer. Use a roller to paint the flat sides of the door and a flat, 2-inch paintbrush to paint the edges. Paint one side of the door first, and then gently turn the door over to paint the other side. Paint the edges last. Wait for the primer to dry before moving to the next step.
Paint the door, using the same steps as before: paint the flat sides of the door first, using a roller, and paint the edges with a flat, 2-inch paintbrush.
Paint on a second coat, if necessary, following the same procedure as in step 6. Wait for the paint to completely dry.
Reattach hardware to the door, and then reattach the door to the frame.