Well I am referring to a period up to about ten years ago.
Hard currency us$ will be required for most transactions apart from fuel. Even if you can use a credit card now, don't depend on it. An availability if a hard currency float is essential if all else fails. Make sure you take plenty of small denomination bills. If you hand over say $400 us for to settle an invoice of $315, they conviently wont have change. Of that you can be sure. Keep the bulk of that cash in a safe place on the aircraft, that should be locked of course and only take off what you really need.
The odd bottle of Scotland's best, never goes amiss either, to get the impossible achieved, depending on the country you are stuck in of course.
For that length of time you need to take precautions against malaria. Certain strains can be a killer, within a very very days. Equtorial regions especially.
Like all all other countries you visit, behave as a guest and not as if you own it.
Not sure how good your fuel carnt card would be in certain countries. You may need to check this out and arrange fuel credits when and where necessary.
Use the broadcast frequency, 126.90? and listen out at all times on this and the freq for the region asigned. If it is still used then it will be found in the Jepson manual.
If you dont have a sat phone, it may be a good idea to set up an account with some outfit such as Stockhom radio, for long range comms. Look them up on the net.
Not really much I can add apart from good lookout as normal and brief well on Safety heights etc.. You will enjoy it.
I am sure others can give better up to date advise.