Sand the surface of the plywood with a fine-grain sandpaper, like 100 to 220-grit sandpaper. Remove nicks and as many other imperfections as possible with the sandpaper, until the plywood surface is smooth to the touch. Then wipe the surface down with a rag.
Use a paint brush to apply a single coat of pre-stain wood treatment. The use of pre-stain treatment or conditioner helps the plywood absorb the stain when it is applied in an even way, so that there are not patches of the stain that appear darker or lighter than other areas of the stained surface. Allow the pre-treated plywood to sit overnight, or at least 12 hours, for it to dry completely.
Apply a coat of the wood stain you want to use. Apply it evenly. Make sure to use long and even strokes to spread the stain and always remember to brush in the direction of the grain. Allow the stain to dry between six and 10 hours.
Apply a coat of clear coal sealant. This will help preserve the stain and will help to give it a finished, decorative appearance.