When travelling to South Africa the easiest and probably cheapest method of getting around is by hiring a car and driving yourself. Cities and towns are far apart and the public transport is not very efficient.
Currently there are no underground or speed/bullet trains in South Africa although a huge project is underway to build a bullet rain between Johannesburg and Pretoria that forms the economic centre of the country.
Other methods of transport include the infamous minibus taxi. These taxis are constantly overloaded and drive like maniacs. When watching them in action it seems like a good idea to stay out of them.
The railway system connects the main cities and their surrounding townships but is not well developed enough for transport inside the cities.
If you visit South Africa only for a day or two for business, the best method of transport is by pre-booking door to door shuttle services, this is the most convenient safest and cheapest form of transport in and around the major cities. These companies can easily arrange for a quick safari to some of the nearby wildlife reserves as well. The pre-booked shuttle services are significantly cheaper than taking a metered taxi cab.