Set the door up on sawhorses or any other waist-high flat surface.
Remove any hardware that's installed on the door.
Use a brush and a rag for stain application.
Shake the stain in the can and then pour some into a shallow dish so you can keep it handy without having to dip your brush into the can.
Focus on one end of the door at a time.
Apply stain first to the sunken parts of a paneled door, using a paintbrush to put down a smooth, even layer.
Put a layer of stain on the strip between the panels, then across the end section (top or bottom of the door).
Stain the areas along the sides and work from the center of the door outward.
Repeat the steps for the other end of the door.
Do the moldings inside the panels last, wiping the stain on with a clean rag and matching it to the rest of the door.
Apply a second coat after the first has dried.