You should leave a copy of all important documents with a trusted person at home who is easy to reach. Try to memorize all of the important details such as passport numbers. If you do lose your bag this information will be very helpful an you will be happy to know it.
Electricity is generally 220/230 volts, 15 amps, and is supplied through either 15- amp three-prong or 5-amp two-prong plugs, in both cases with round pins. If you are planning to bring anything that is electrical, you should also plan to bring an adapter or buy one at the very least. Generally, the 110V video chargers work safely on the 220V supply. You will find television is on the PAL system.
Bring spare glasses, and bring a copy of your prescription so that they can be easily replaced just in case they are lost, damaged or stolen. If you regularly wear contact lenses then consider using some disposables for the short trip, especially if you are planning on river rafting, diving or other such activities. Do not forget your glasses too even if you wear contacts regularly as the dry and dusty environment of some game farms might be irritating to your eyes.
Remember to pack a camera because you will want to save your wonderful adventures on film. You can buy disposable cameras or batteries in any city if you like. Bring your mobile phone with you or rent one when you get there. South Africa does use the sophisticated GSM network and most cell phones will work over there, as long as they are un-locked.
Many rental car companies will also rent you a phone. It is possible to buy a SIM card at the airport, supermarkets or other such outlet. Make sure you have your passport and an address of where you are going to be staying if you want to buy a SIM card in this fashion because the network operators are required by law to save the details of any new SIM card holder.
If you have forgotten anything please do not panic. This is not the middle of nowhere and you can easily buy almost anything you need. You will probably even get it at a good price. You will likely want to do a large amount of travel & exploration while you are on your trip. Remember that it is safe but like anywhere else that there are wild animals you must stay in the clearly marked safe zones. Should you accidently find yourself outside of these zones you should hurry back to a protected area for your own good. There are plenty of guides that can show you a wilder side of Africa but that is best left to the professionals.