Minibuses come in two forms - yellow with green roofs (government run) - and yellow with red roofs (private). They can accommodate up to 16 people.
The private ones can be fast and convenient. The destination placed on the front is usually written in Chinese characters and drivers rarely speak English so some familiarity with the route and Cantonese is required. Routes are not always fixed and passengers may get on or off anywhere. You must call out in Cantonese your alight point as you approach. Pay the driver as you get off, small change is sometimes provided. Or pay with your Octopus. Fares range from HK$2 to HK$20.
The yellow and green minibuses have specific routes with fixed fares. Drop your coins in the box as you get on or pay with your Octopus. Fares are from HK$2 to HK$20. Again you must call out when you wish to alight.