In general all bus fares in HK are based solely on where you get on the bus. So sometimes it makes a significant difference which service you get on when more than one runs between the same two intermediate points. You should try to get on a bus near the end of its route rather than one near the beginning, if you have a choice.

However, there are a few exceptions to this where some individual routes have what are known as "stage fares". You can only access these using your Octopus card and you represent it to the card reader when you get off as well as when you get on. The bus company websites tell you about them, and also the posters which are on the bus stops for that route.

One example is the number 6 route to Stanley. It is more or less the only way for people to get by bus from Central to Wong Nai Chung Gap and the area around the Cricket Club, Parkview, etc. But this is only halfway to Stanley, so there is a stage fare on the number 6 if you get out at the stops up Wong Nai Chung Gap Road - from memory I think you save about 30% of the fare.