Remove the door from its hinges by pulling the pins out and lifting it up and away from the frame. Set the door on a work surface, such as two padded sawhorses.
Remove the hinges and doorknob from the door with a screwdriver.
Wash the door with trisodium phosphate to remove any grease and dirt. Dry thoroughly.
Fill in any flaws or cracks in the door with wood filler and a putty knife. Work filler into the hinge screw holes. This allows you to install the new hinges without having to cover the old ones. Allow the filler to dry according to the package instructions.
Apply a stain-blocking primer onto the door with a sponge roller or bristle paintbrush. Use a heavy, even layer of primer to ensure the wood grain won't show through. Allow the primer to dry according to the package instructions.
Paint the door with an enamel-based paint using a sponge roller or bristle paintbrush. This type of paint comes in many modern colors, such as gunmetal or black, and gives the door a sleek, polished finish. Allow the paint to cure. Apply a second coat if desired.
Attach new doorknobs and hinges to the door. Use hinges and doorknobs that go with the contemporary look, such as chrome or stainless steel.
Rehang the door in the door frame using the new hinges.