What others have mentioned already and.....
1. Determine what PG species you're interested in. There are 70+ different antelope species alone with 50+ subspecies with, hogs, predictors, and some primates etc. on the African continent. Many are only native to certain areas/regions. However, with high-fence and put/take done to greater/lesser degrees in most countries, you can sometimes take normally non-native species in a given area/region as well. This will help you narrow your focus a bit and bring you to the next choice.
2. Do you want to hunt totally free-range/fair chase or high-fence or some combination of the two within reasonable proximity of each other. These first two will help you narrow down the country.
3. As mentioned - rifle, archery or even big bore handguns in RSA and perhaps country specific caliber minimums.
4. Next you can start researching booking agents and outfitters and PH's in those countries and areas you've defined above.
5. Then you'll have to decide if you're interested in a set price "package hunt" or what I refer to as an "ala carte" hunt where you pay a daily rate and individual fees per animal.
6. Next, are you planning to go alone, with spouse/family or a hunting friend etc. and do you want to include any non-hunting sightseeing days. Some of this will help you decide if you want a traditional tented camp or fixed camp and lodging or more luxurious to accommodate a non-hunting or limited hunting spouse.
Lots of variables to start digging into. The first three will help drive the rest of your research.
