Massaging with light pressure removes dead cells. For the face, try a soft washcloth or a Buf-Puf. As for granular scrubs, the gentler the better. Soft synthetic beads should be plentiful in the formula (look for "polyethylene" near the top of the ingredients list). For the body, coarser scrubs and loofahs are fine as long as skin is not dry, irritated, or cracked. Exfoliating manually is safe once a day or a couple of times a week, but scrub only for about a minute, apply light pressure, and use a good moisturizer afterward. Cost: $4 to $60.
These acids, which come in varying strengths dissolve the glue-like bonds that stick dead cells to the skin's surface. Using an acid at night in conjunction with a manual exfoliator in the morning sweeps away the loosened cells faster than either method alone. Acids exfoliate deeper than scrubs (although still superficially), and because the application is uniform (there's no scrubbing involved), the results are more predictable.
If your skin is oily, use a BHA, because the hydrating effects of AHAs can make oily skin look shiny. Start with a low-strength formula; if your skin tolerates it well, after two weeks you can begin alternating every other day with the next strongest formula. Cost: $4 to $50.