Figure: AFI Region, from Eddie's notes.
Regional differences from the ICAO standard can be found in ICAO Document 7030 and your Jeppesen Airway Manual. Both of the sources, however, can be out of date. See International Operations Manual / Regional Introduction for ideas about getting up-to-date information.
As countries around the world update navigation systems and procedures, it becomes increasingly important to speak with somebody who has been to the airport recently or have a contact in country with local knowledge. As we say in the military, there is no substitute for boots on the ground.
What follows comes from the references shown below. Where I think it helpful, I've added my own comments in blue.
This region is moving from a mix of navigation requirements to the system of Performance Based Navigation outlined in ICAO Document 9613. Current navigation requirements are available on Jeppesen Airway Manual Air Traffic Control pages and Chapter 4 of each region covered by ICAO Document 7030.
[ICAO Doc 7030, §AFI, ¶126.96.36.199.] RNAV 10 (RNP 10) Area of applicability:
Not all countries are WGS-84 compliant. For two examples of many:
More about this: International Operations / World Geodetic System 84 (WGS-84).
[ICAO Document 7030, §AFI, ¶4.2.1] A minimum vertical separation of 300 m (1 000 ft) between RVSM-approved aircraft shall be applied between FL 290 and FL 410 inclusive in the following FIRs: Accra, Addis Ababa, Antananarivo, Asmara, Beira, Brazzaville, Canarias, Cape Town, Dakar, Dakar Oceanic, Dar es Salaam, Entebbe, Gaborone, Harare, Johannesburg, Johannesburg Oceanic, Kano, Khartoum, Kinshasa, Lilongwe, Luanda, Lusaka, Mauritius, Mogadishu, Nairobi, N'Djamena, Niamey, Roberts, Sal Oceanic, Seychelles, Tripoli and Windhoek.
[ICAO Document 7030, §AFI, ¶6.2.4]
More about this: Procedures & Techniques / Reduced Vertical Separation Minimum (RVSM).
Some countries use a mix of QNH and QFE. For one example of a decreasing list:
More about this: International Operations / Altimetry, Metric, QFE/QNH.
Transition Altitude / Layer / Level procedures are nonstandard in several locations. For one example of many:
More about this: International Operations / Transition Altitude / Layer / Level.
Each country departs in some ways with the ICAO standard and common US practices. Pilots should always refer to the Jeppesen Airway Manual, Air Traffic Control, State Rules and Procedures pages for each country on their itineraries for differences with ICAO Standards, Recommended Practices and Procedures. More about this: International Operations / US versus ICAO.
The following are a sampling of some of the differences, there are many more. You should check the Jeppesen Airway Manual State pages for every country you takeoff, overfly, or land.
[ICAO Document 7030, AFI, Paragraph 188.8.131.52] Changes to flight levels must be made in controlled airspace. Pilots should anticipate the need to climb and understand flight level changes may not be possible in some airspace.
Many countries have exceptions to ICAO standard lost communications procedures, as listed in their individual Jeppesen Airway Manual, Emergency, State Rules and Procedures pages.
More about this: Abnormal Procedures / Lost Communications.
Some countries have non-standard position reporting procedures. For one example of many:
Some countries employ Strategic Lateral Offset Procedures (SLOP) over domestic airspace. For example:
More about this: International Operations / Strategic Lateral Offset Procedure (SLOP).
Some countries have uncontrolled IFR airspace requiring a "listening watch" procedure on air traffic advisory service frequencies. For one example of many:
For more about this: International Operations / Traffic Information Broadcast by Aircraft (TIBA).
ICAO Doc 7030 - Regional Supplementary Procedures, International Civil Aviation Organization, 2008
ICAO Doc 9613 - Performance Based Navigation (PBN) Manual, International Civil Aviation Organization, 2008
Jeppesen Airway Manual