Hong Kong has two kinds of Minibus： Green Minibus and Red Minibus. Not only they serve different routes but their operating system are totally different.
In general, the Minibus seating capacity is 16 and destination are displayed on the front window (both in Chinese and English). The English characters are sometimes very small and hard to spot/read when the Minibus is passing by. Similar to the big buses, customers have to pay the fare when entering the Minibus either swiping the Octopus card over the fare receiver or tendering the exact fare into the coin box next to the driver. If a passenger would like to get off, he or she needs to indicate this one to the driver which can be for a foreigner quite difficult –since most of the drivers don’t speak and/or understand English. There are no bells are buttons to be pushed (only a very small numbers of vehicles are equipped with this) and passengers usually need to shout: “Next stop please!” to get off. If a Minibus is complete full and all seats are taken, the driver will not stop at intermediates stops unless one of the passengers wants to get off. The driver usually will give some kind of a hand signal indicating to wait for the next Minibus. Since the Minibus fleet is quite big and therefore the frequency quite high too, passengers won’t need to wait to long for the next Minibus to come along.
Here you can find fares, routes and information about the Green Minibus.
The Red Minibus works a little bit differently than their Green counterpart. They don’t operate on a schedule and set their own fares which can rise during peak hours or due to worsening weather conditions quite quickly. In most of the Red Minibus customers are required to pay the driver when exiting (!) and usually have to tender the exact fare since they don’t have any Octopus system installed. The transportation of the Red Minibus are not particular “visitor-friendly” since the schedule, route, frequency and fares are not really transparent from someone outside.
Some piece of advice: I have taken many Minibus over the years and have to admit that some rides can be quite rough due to the high speed and/or the limited leg room. Although, the driving speed should not exceed 88km/h, most of the drivers will drive faster and exceed this speed limit. Visitors should take into consideration that due to this speeding behavior, Minibus is involved into accidents and crashes above average.