These are simply listed in point format to make it easier for you to read right through to the end. Of all the reviews I've written online these are my major points to consider.
Book in advance
The best way to find a cheap flight is by booking early. Do not wait until the last minute or else you will be charged "last minute" fees, which are normally exorbitant. The earlier you book the better. Try 10 weeks in advance if you can.
The best time to travel is midweek. That is, from Monday to Thursday. After this it can get really costly. I mean the weekends are considered peak time since everyone is traveling - if you want to fly cheap to SA, avoid weekend flights.
Book indirect flights
One thing is certain - direct flights are pricey. This comes with the convenience of direct flying. If you are looking for the cheapest flight then do not even think about direct flights.
Travel in winter
If you ever compared flights in summer and winter then you'd know that winter prices are cheaper. This is because winter is considered off peak in South Africa i.e. midyear since we are in the Southern Hemisphere.
Travel at night
Actually most of the flights are night flights. However there are also day-flights, which you must avoid if you want to fly cheap. However, it is always best to compare these flights just incase there is a discount being offered by the day-flights.