How to Stain an Exterior Door

Remove as much of the door hardware as possible, including peephole, kick-plate, lock set and door handle. Remove the weather-stripping.

Sand the door smooth. Use an electric rotary or palm sander for the fastest results, and folded sandpaper for corners and details an electric sander won't reach. Finish by hand-sanding in the direction of the wood grain, using 150-grit sandpaper. This removes the cross-grain scratches left by an electric sander--these will show up when the door is stained.

Apply a pre-stain sealer if the wood is soft, such as pine or birch, to ensure the stain goes on evenly without blotching. Oak does not require a pre-stain sealer. Let it dry according to label directions; usually eight hours. Protect the weather-stripping with blue painter's tape if you didn't remove it earlier.

Brush on the stain liberally, making sure to fill in all the grain. Don't worry about getting it on smooth surfaces like glass or hinges--it will clean off when you wipe the stain. Let the stain sit for five to 10 minutes.

Wipe the stain with a lint-free rag until the surface is clean and buffed, and the color even. Let the stain dry for at least 12 hours or as directed on the label.

Spray or brush at least two coats of varnish or polyurethane over the stained door. Marine spar varnish will provide the best protection against extreme weather conditions like rain and sunlight, but it takes a long time to dry between coats. Sand each coat of varnish lightly between coats with 180-grit sandpaper.

Clean, polish and replace the door hardware.