In Johannesburg it is unsafe - this is so. But if you still decide to visit this city, then you should follow certain rules to make this visit as calm as possible.

First, there is no such thing as a "walk". To move better by taxi or together with the group on a tourist bus.

Secondly, do not visit unfavorable areas (Soweto, Alexandra and others).

Third, do not leave valuables or bags in the car in sight.

And, fourth, do not "shine" with money, technology and ornaments. In general, it's better to move around in protected places.

As much as the tourist will follow the recommendations for staying in the country!