What is GRIT?
The grit or grade of sandpaper is based on the number of sand granules per square inch of paper. The higher the number, the finer the grade. Lower-numbered grades denote coarser sandpaper.
Type of Sandpaper
Keep In Mind
Always sand in the direction of the grain--never perpendicular to it or at an angle.
Scratches made by sanding against the grain will look unattractive on the finished piece and will be particularly noticeable after staining.
Wood dust from sanding will cause problems if it's not removed from the surface before staining. Dry rags or brushes aren't the most effective tools for removing dust. Instead, use a tack cloth, a sticky piece of cheesecloth made especially for this purpose.
Always wear a respirator and safety goggles/glasses when sanding.