Hammer down any nails that protrude past the surface of the steps, baluster or railing.
Fill any cracks in the wooden stair steps, balusters and railing with expanding urethane glue. Smooth the urethane glue into the crack with a plastic putty knife. Wipe away any excess glue with a moist cloth. For cracks in metal balusters and railings, use a metal filler.
Remove any gunk between the boards that make up each step, using a butter knife.
Sand the finish on the stair tread, baluster (if wood) and railing (if wood) with a belt sander. With light pressure, push the machine back and forth on the stair. Be careful to sand lightly to avoid removing too much of the surface.
Vacuum or sweep away all debris from the stairs. Use a damp mop or cloth to pick up any excess debris. Allow the stairs to dry thoroughly.
Wipe wood stain on the stair tread and riser, balusters (if wood) and railing (if wood) with a dry cloth. Stain will often enhance and renew the staircase. Allow the first coat, and any additional coat of stain, to dry before applying a finish coat.
Wipe clear finish coat over the steps after the stain has dried. Sand down the clear finish coat after it has dried using medium-grit sandpaper. Apply a second coat of clear finish and allow it to dry before sanding it down and applying at least one additional coat.