In order to gain entry into South Africa, you will need a valid passport or travel document that covers the whole of your intended stay.
For Visa requirements, see http://www.home-affairs.gov.za/Counties Exempy from SA Visaa.html.
Please note that you have to have at least two blank pages in your passport. This requirement is strictly enforced, and you will be refused entry into the country if it is not met.
Yellow fever certificates are required if the journey starts or entails passing through the yellow fever belt of Africa or South America.