Sand paper or buffer:
If the scratches do not go deep down the wood, you can easily do with a scuff sand done with a floor buffer. For scratches that are deep and for a very rough floor, you will have to use sand paper to remove the top layer of wood. Using a floor buffer is easier, less time consuming and inexpensive. In this guide, we are using a floor buffer and those who want to use Sand paper read step 5.
Rent a floor buffer. Attach the heavy screening pad to it and start moving it over the floor, in the direction of the grain. This will remove the top layer of the old finish. Once you have covered the entire floor, use a vacuum to clear up the powder.
Attach medium screening pad to the floor buffer and cover the floor again. Vacuum again.
Repeat again with a fine screening pad to get perfectly smooth surface. Vacuum the whole room now to clear away the powder and dust.
Use a paintbrush top apply a thin layer of polyurethane over the wood slowly. Keep the direction along the grain. Let this coat dry for six hours. Once dry, sand off the wood with fine sandpaper to dull the surface. Vacuum again.
Apply another coat, let dry and sand again. Vacuum off the powder.
Apply the last coat of polyurethane and this time let it dry for twenty four hours.
If you believe your floor needs a harder treatment, use sand paper to sand it all over. Use 32-grit sandpaper at first over the lay of the grain. Vacuum the dust. Now use a 60 or 80 grit sandpaper. Vacuum again. Finally sand with 100-grit sandpaper. Vacuum the dust and clear the surface with a wet cloth.
Treat the floor to polyurethane now as in the 4th step above.