Hong Kong does not have the best climate in the world, we know that. Either it’s too hot or too cold and maybe raining at the same time.
I found the public buses to be the best way to explore Hong Kong beyond the standard tourist sites.
They are cheap, air-conditioned, have a roof top, run frequently and all over the islands. Most of these buses are double-deckers too, so make sure to enter at the first station to get the good view.

This is my list of my favorite bus lines through Hong Kong. I will regularly update it, so do come back! Also, feel free to suggest your own routes!

Drinking on Public Buses:
Eating and drinking is both prohibited on all public buses. Especially bringing in smelly food or making a mess will earn you the angry stares of other passengers, but bringing in a bottle of beer or some bubble tea is rarely frowned upon. I admit that taking bus N11 at night having a cold Tsingtao in your hands, and staff very rarely sanctions ‘illegal-though-considerate-behavior’, so be respectful that it stays that way.

Hong Kong Island:

Kowloon / New Territories:

N11	31$	Macau Ferry <–> Airport This is a ride to dream in. It is both a pleasure to and from the airport, and almost romantic, displaying the busyness and loneliness of a city that is both so very international and isolated. You will hardly find people talking inside the bus, and yet it might be full. It serves both airport employees and budget travellers, and because of that displays globalization much better than the inside of the Cathay Pacific lounge. The bus goes through the airport services district, makes a turn through Tung Chung, takes the longer route around the harbor (better views!), cuts through Tsim Sha Tsui and the Central Harbor Crossing to Causeway Bay and then goes along Hennessy and Des Voeux Road to the Macau Ferry Terminal. It’s pure melancholia. Time: 75mins
967	21.4$	Admiralty –> Tin Shui Wai As much as the N11 reminds you of trade, industries and steel, the 967 will show you the quiet and suburban green refuge that the New Territories provide. After going through the Western Harbor Crossing and past the Port, the 967 cuts through Tsing Yi and Tai Lam and opens Kowloon’s backyard to you. It’s green, there are fewer houses, and the suburban villages around you don’t seem like Hong Kong at all. Before the bus arrives at Tin Shui Wai, get out at the Hong Kong Wetland Park and enjoy the Pearl River Delta in its purest form. Time: 75mins
Red Minibus	14$	Mong Kok -> Kennedy Town Dubbed the Midnight Death Wish Ride, this Minibus goes between Mong Kok and Central faster than the MTR. It’s easy to catch from Nathan Road just a little south from Mong Kok station, near the large signs advertising Saunas below. It does not accept Octopus cards, so do have change ready (you pay when you get out). All minibuses are equipped with a display that shows the passengers the current speed. It also beeps when going faster than 85 kph, though in this ride, the beeping seems to act like cheering to the driver, and quality measurement to the passengers. When you want to get out, just scream.

Lantau:

Here are a few useful resources on bus lines in Hong Kong.
Wikipedia has the most extensive collection of bus lines.
Google Maps allows you to calculate directions by public transport.
CityBus and First Bus show you their bus route conveniently on a map.
The Kowloon Motorbus Company shows you the starting- and end-point of each route on Google Maps
The New Lantau Bus Co shows you on a map all its routes across Lantau.