Take the door off its hinges to properly paint the door and trim. Use a screwdriver to remove the hinges from the door and frame. Place the loose hardware in a plastic bag. Remove the doorknob and latch assembly and place them together in a separate plastic bag. Lay the door on a flat surface.
Patch holes and cracks. For hollow core doors use a wood patch kit. For solid core doors or doors with small cracks, use wood putty that is similar to the color of the door. Work the putty into the crack with a putty knife and scrape away any excess. Allow the wood patch kit or wood putty to dry according to the manufacturer’s instructions.
Sand the entire door and frame using medium grade sandpaper. When sanding, remove the finish but not the actual stain on the wood. Wipe away dust with a tack cloth, and then sand the door and frame with fine grade sandpaper. Wipe away dust and make sure the patched surface is completely level with the rest of the door.
Use a paintbrush and water-based latex paint to paint the door and frame. Apply one light coat, and paint with the grain of the wood. Allow the paint to dry for approximately 4 hours. Flip the door over and paint the other side. Let dry for approximately 4 hours. Apply a second or third coat, if necessary.
Attach the door to its frame. You may need a friend to help hold the door during this process. If paint scrapes occur during this process, touch up the area immediately with fresh paint and allow it to dry for approximately 2 to 3 hours.
Attach a new doorknob to the door. Make sure the knob fits with the home's décor. Traditional or antique interiors may be replaced with crystal knobs, while contemporary interiors can be replaced with brushed chrome or nickel knobs.