After reaching the country of destination, there are so many options to consider to move from one side to the other. To visit and discover all the destinations of your trip, you can travel by plane, train, ship, bus, car or even on foot. Usually, the means of transport from one place to another are chosen at the time of making your travel itinerary. Much depends on the time available, on the money you intend to spend, but also on your personal travel preferences.
It is necessary to analyze the characteristics of the territories you intend to visit to establish the means of transport that are most suitable. It is not always enough to rely on personal preferences because many other factors can make it difficult to do so. There are modern countries where all options are open and the choice is based on a mix of all the above factors. However, often, especially in the less developed countries, the choice for means of transport is not so simple and must take into account the difficulties posed by the territory.
Infrastructure can make travel difficult with private rental vehicles. Furthermore, sometimes the railway lines are almost non-existent or not well extended. At other times, the absolute lack of a competitive market and the low demand can cause rental prices to rise at high levels compared to market economies. All that said, it must be considered that in the case of a breakdown it could be very difficult to receive assistance in a reasonable short time.
The most reliable means of transport par excellence in the least developed countries are buses and ships, depending on the territory you are going to travel to. They are also the cheapest means of transport and therefore definitely preferred by those who travel on a small budget.
There are so many infrastructural differences from country to country and therefore it is very difficult to set rules for traveling. Some suggestions may come from research on specialized websites, but most information comes from personal experience.