Summarize this article:

Make sure that the room is devoid of any furniture, window treatments and wall hangings. If the floor continues into a closet, make sure to empty it. Be cautious not to drag furniture across wood floors. Heavy furniture may scuff the hardwood and leave marks. Insert a small piece of wood behind the pry bar to provide leverage, and to prevent damaging the trim pieces. Seal all of the openings–electrical outlets, vents, and light switches–with masking tape. Cover the light fixtures with trash bags, and secure them with masking tape. Separate the room from the rest of the house by taping the door shut or hanging plastic sheeting in the doorway.  You may find gaps or gouges in the wood which need to be filled. Apply wood putty according to the manufacturer's instructions. Allow it to dry thoroughly before proceeding with your finishing. You should also protect yourself from sawdust and stain fumes by wearing a respirator. Any water spots where the wood has turned black can be treated by mixing a 50-50 solution of bleach and water to remove all or nearly all black spots.

Summary:
Prepare the area that is going to be finished. Remove trim using a pry bar. Protect the room from sawdust and stain fumes. Vacuum the floor thoroughly to remove any dust and debris.