Refinishing wood floors is not an easy project to take on, but it is well worth it in terms of satisfaction and beauty. Some of the work will depend on what condition your floors are in now. You'll need to prepare the wood by removing any nails or tacks and securing any loose planks. Rent a drum sander and edger. Sand with three consecutively finer grades of sandpaper. Clean up all sanding dust. Apply stain (or not) and finish. The end result, if you take time and care, will be very rewarding.