Public transport differs all over the world. There are different standard depending on the country you are in and the types of transport that are available. From buses and trains to tuk-tuks and horses, it all very much depends on the part of the world you choose.
As a rule, there will be lots of timetables and clear transport options in Europe. Other parts of the world may be more challenging, and you may be better off booking transport with a private tour operator for reliability.
If you want to know what to expect, read a guidebook about the country you are visiting. This should tell you some of the basics, like how to book train tickets and how to get a bus. Etiquette differs vastly, with some bus drivers expecting you to pay as you get on and others coming round to collect cash. Just make sure you know what to expect.