On top of the the very good advises given, i would add few things :
Remember every ATC will ask your t-off time, ET for all points in its control zone and ETA destination. So be ready with a log after take off. But there is no hand-over to next control : at some stage, you 'll have to get in contact with both centers (if you are in such a busy area with 2 reacheable but geographically separated vhf frequencies). Start every request with DME to station (and radial if out of airways, and altitude crossing if not stable) . It usually supress the need for the next 4 radio calls. If low level, auto information on 118,1 works pretty well in the area. Remeber a lot of people speak a really poor english in this part of the world (like me). Try to stick to standard radio procedures and speak slowly. Monitor the other aircraft's radio transmissions to make sure atc do not send an aircraft on collision course with you.
Make sure your overflight and landing clearance # is within reach during the flight as atc will ask you prior to clear you to proceed to land !
Never overfly military base and "Palais presidentiel"
Don't trust notams about fuel availability or airport status.
Asecna weather office is quite good. But don't trust too much the taf. Weather patterns are very recurrent but not very predictible. Fasten your safety belt
And be ready for a gps overlay procedure as navaids can be down without any notice. BZ vor is currently down ! And control ask you your gps radial and distance...
Check the fuel you asked for is really pourred in your tanks. Remember push back is not likely to be available. So park in a position you can taxi out on your own. Ask if the nearest fuel pit is working before you shut down, you'll save a cycle...
BGF is very quiet : few schedule flights and 3 or 4 light turbo-props flying low level in the country. ATC could be lost with more than 1 aircraft inbound... But you can suggest traffic separation solutions if you have better ideas
Closest IFR alternate is Gbadolité, 145 Nm (without fuel and you don't want to go to RDC anyway) or Mbandaka (fuel but still in DRC) or Yaoundé in Cameroon which is far far away .
BZA : much more busy, be ready to hold at pondo. Specially at sunset. Everybody try to get back before night to avoid to be charged for lights... It's a rush with same freq for gnd, twr and approach... Kin is not a suitable alternate neither. So plan for PNR as altn...
Avoid ice cubes in your coke (usually made of non filtered water), discuss the taxi fare before you board the car, get a lot of change in small denomination, change your hard currencies to CFA in any lebanese shop or restaurant.
Same value in west and central africa, (but different notes) the CFA is actually an hard currency. Its value raised by 50 % toward the dollar since 2002 ! That's because € to cfa is fixed rate (655,957 rounded at 650)
$ to cfa was 420 to one last week.
Do not accept straight away handling without knowing what services you'll be charged for. Unless what you are gonna end up paying 1000 $ for a pair of shocks (removed from your aircraft when the next plane comes in anyway)
On un-controlled airport, make a low pass before you land to check for runway conditions and/or obstacle, people, car, elephant, wheelborrow on the runways. On controlled airports, be cautious for the exact same reasons on short final... (even on large int'l airport). Allways be ready to go around.
Take a roll of toilet paper everywhere with you... you never knwo when !!!! happens. But you know there won't be any paper where it happens !
And don't get married too fast during a hot night with the first lady you meet... (try several one before...
no, I didn't say that)
A great sense of humour is a big asset.
Have fun !