Wood to be finished in natural or stained color must be prepared thoroughly before starting the finishing process.
It should first be dusted off with a duster brush or a broom in the case of floors. Then all spots of plaster, dirt or grease need to be removed. Usually these spots will come off with a washing over with benzine, using a putty knife to scrape off as much as possible. If the wood is oak, walnut or other open-grain variety, be particularly careful to remove dirt, lime and grease from the pores of the wood. When these spots are not properly cleaned, the stain does not take hold and penetrate and the finish can be spotty in appearance.
New surfaces which are to be finished with paint and enamel ought to be cleaned well, but there is no need to be so particular about light stains. All loose particles on the surface should, however, be removed. Dark stains from rust or other substances on new surfaces should be bleached out before being finished in natural or colored stains. After cleaning the new surfaces they should be sandpapered if the finish is to be natural or colored stains. This is not necessary for paint or enamel finishes.
If water stain is to be used many finishers prefer to brush or sponge on a coating of water before sandpapering. The water stain will raise the grain of the wood, making little wood fibres stick up all over. If the surface is wet in this way before staining, the water stain does not raise the grain so much and the second sandpapering is very light. If the water wetting is not done before staining with the sandpapering operation on some woods must be done so heavily that some of the stain color can be cut off the wood. This sandpapering operation on new wood before or after wetting should be done with No. 0 and No. 00 paper, depending upon the roughness of the wood.
Sometimes it's a good idea to go over the wood first with a No. 1 paper and finish up with a finer grade. After sandpapering the surface should be well cleaned with a duster brush on ordinary jobs. On fine furniture and cabinets more effort should be spent to remove every particle of dust. In furniture factories the dust from sanding is blown out of the pores with compressed air. Wood to be finished in very light natural color such as, maple, birch, etc., are often bleached before any finishing coats of filler, varnish or shellac are put on. The bleaching raises the grain of the wood and a thorough job of sandpapering must be done after that process.
New surfaces to be finished in natural or colored stains and which show cracks and holes should be filled to remedy these defects. Plaster of Paris soaked in water is preferred by many finishers for this filling because it will absorb stain and also will take on the coloring given by filler. Other putty does not absorb color. On stained finishes as a rule the putty is put into the cracks and holes after the stain is dry. After putty is dry it should be sandpapered down smooth and clean. Then the surface should be cleaned up around the repairs.

Preparing wood for finishing can be difficult and laborious, for tips and ideas go to http://www.wood-finishingonline.com, a comprehensive website that deals with every aspect of wood-finishing.