Glossy leather belts dull with time, even if you keep them clean and wear them only occasionally. You can easily bring new life and high gloss back to most leather belts; in fact, when you are finished polishing your belt, you may be amazed at the results. You'll need just a few simple, inexpensive items and a short amount of time. Plan a little ahead of an important event, however. You may not be able to wear the belt right away. Generally, allow the polish to cure on the belt at least overnight; otherwise some color from the polish might rub off on your clothing.
Clean your leather belt before polishing. If it is not visibly dirty, wipe it down with a soft cloth; otherwise, apply leather cleaner (the same kind you use for leather shoes) to a soft cloth, and rub it over the belt. Wipe it again with a dry cloth, and allow the belt to dry before continuing. According to Mrscleanusa.com you can, alternatively, clean leather shoes and belts with white vinegar and water (mixed 50/50, applied to a clean cloth and rubbed over the belt).
Choose a polish. You can use the same polish you’d use on leather shoes. Choose either the wax or the liquid kind that comes with a sponge applicator. Choose a colored polish to match your belt color, or, if you use the wax, choose a neutral color. If you use the wax, you may want to wear protective gloves because it tends to cling if you get it on your hands.
Apply polish to the belt. If you are using the wax polish used on shoes, open the lid and, grasping one corner of a clean cloth, dip the cloth in the wax to retrieve about a quarter-size dollop. Rub this into the outside (the part that shows when you wear it) of the belt. Use more wax polish if necessary. If you are using the liquid polish, use the sponge applicator to rub the polish onto the belt. (Squeeze the bottle to coax the liquid out.)
Buff the belt with a soft cloth. Remove excess polish using this cloth, and switch to another clean cloth. Buff the belt until it is shiny.
Instead of shoe polish, you can use beeswax, as suggested by mrscleanusa.com: Rub it on as you would a wax shoe polish. Let it sit for a while, and buff it with a clean cloth.