That depends on the quality of the leather and whether or not it has already been treated with a good conditioner and/or moisture protectant. Generally, you don't want to use anything other than products that are specifically designed for leather goods such as shoes, purses, and jackets. Any good leather cleaner will work well (I would avoid anything that is made for a specific color of leather, because they can be tricky or may alter the color of the leather). Also, it is a good idea to follow the cleaning with a conditioner to keep the leather from becoming dried out. Sometimes you can find a conditioner that will work well as a cleaner for minor marks and blemishes.
Apply a small amount of cleaner to a clean, lint-free cloth and lightly rub the leather in a circular motion. Wipe the leather dry and follow up with the same procedure with leather conditioner.