The Tambo International Airport is just 21kms away from the city centre and is the busiest in Africa connecting to other cities. The important international hubs like Paris, London and Frankfurt is well connected too. From the airport you can either take the Gautrain which is cheap or a taxi or a Metro rail suburban train to Joburg.
Park train is the central station of the city and the long distance Spoornet trains are safe and convenient. Spoornet connects you with all the major cities like Pretoria, East London etc. The metro rail and the Gautrain run towards Pretoria, Soweto and Springs.
There are long distance buses like Greyhound, Translux and Magic Bus which provide services to and from Johannesburg.