Strip the original paint. If the steps are made of concrete, stick with a solvent, such as mineral spirits or paint thinner. If the steps are wood, you may use a solvent or sand the stairs down with medium-grade sandpaper. If you sand the steps, sand them a second time with fine-grade sandpaper.
Wash the steps with trisodium phosphate. Use 1/4 cup of TSP for every gallon of hot water. Scrub the stairs with this solution, and rinse with a cloth and fresh water. Allow the stairs to dry.
Stir the primer thoroughly until it is well-incorporated and uniform in color. Pour the primer in a paint tray.
Start at the top of the stairs and work your way down. Paint the primer into the corners and edges of each step with a 2-inch paintbrush. Apply primer to the rest of each step with a paint roller.
Allow the primer to dry. Mix and apply the paint as you did with the primer. Allow the paint to dry and apply a second coat if desired.
Seal the steps with a protective top coat, such as polyurethane. Wood and concrete sealers vary by manufacturer in directions for mixing, applying and drying, so read the labels carefully before you use them.