Cedar is one of the most commonly used wood species. It's soft, affordable and multipurpose, and it's used for exterior and interior purposes. Cedar dust can be a health hazard. Wear breathing and eye protection when sanding cedar. Cedar also may have knots that can come loose. Check for loose knots before proceeding with any project.
Cedar is soft. Unless the cedar has deep scratches, gouges or planer marks -- lines running perpendicular across the grain -- cedar should be sanded by hand. Power sanders remove material fast, almost too fast for finish work. If you do need to sand it with a power sander, use an orbital sander with 100-grit sandpaper. Keep the sander moving, using circular motions to flatten and smooth the surface. Don't allow the sander to remain in one place. When the surface is consistently smooth, stop sanding and proceed sanding by hand.
Finish sand the cedar by hand to remove small defects or to remove small circles or scratches if the cedar was sanded with an orbital sander. Start with 100-grit sandpaper, using short strokes parallel with the grain. Sand forward a few inches at a time, overlapping the previous strokes with each new stroke. The sanding is complete when the surface is smooth and covered with a light dust. The cedar can be finished at this point. For a smoother, glassier finish, install 180-grit sandpaper on the hand block and sand it again. There's no need to sand it again with finer grits.
If the aroma wears thin in a closet or chest, lightly sand it by hand with a folded piece of 100-grit sandpaper. When you begin to smell the cedar, you've sanded it deep enough. Repeat sanding over the remaining wood to revitalize the closet or chest.