Unlike mainland China, you won't need a visa to get into Hong Kong. The bad news is you will need one to get to Macau or mainland China from Hong Kong.
Flying
Direct flights leave to Hong Kong International Airport (Chek Lap Kok) from every continent in the world except South America. Neighboring Asian cities like Singapore, Tokyo, and Beijing have at least 10 flights every day, and many North American and Europe cities have at least one flight a day. Hong Kong's airport is third busiest airport in Asia (after both of Tokyo's), and is second in cargo traffic only to Memphis.
From the airport you can take the Airport Express train into the Central district. It's a 23-minute ride, costing HK$110-180 for a round-trip ticket, and baggage handlers are there to help you with heavy luggage. No need to tip!
You may want to invest in an Octopus card, which is a proximity card very similar to the London Underground's Oyster card. For HK$220, you can buy the Airport Express Tourist Octopus 3-Day Hong Kong Transport Pass, giving you a ride on the Airport Express, 3 days of unlimited travel on the MTR (subway/metro), and you'll get a $50 deposit back when you return it.
Airbuses are cheaper but slower. The A11($40) and A12($45) go to the Island, while the A21($33) goes to Kolwoon. If you want to go even cheaper, take the S1 bus to Tung Chung ($3.5) and catch the MTR for a cheap ride to the city.
A cab from the airport will run you $300. If you're with three or more people, it's cheaper than the Airport Express. Taxi laws are strict on charging according to the meter, but baggage and tolls are extra.
Even tourists will want to buy an Octopus card. Octopus cards are Hong Kong's version of London's Oyster cards, and can even be used to pay for convenience store purchases and the like. Adult Octopus cards will run you $150 including a $50 deposit, but they'll charge you $7 for returning it less than three months after you bought it. You'll also enjoy a discount on MTR trains by using it.
MTR
Kong Kong's Mass Transit Railway (MTR) is fast, but expensive. There are five lines: the Tsuen Wan Line (Red) runs from Central to Kowloon and down Nathan Rd towards Tsuen Wan in the New Territories; the Island Line (blue) runs along the north coast of the Island; the Tung Chung Ling (orange) which runs to Lantau, plus the green and purple lines which most tourists won't encounter. The pink line provides service from Sunny Bay to the new Hong Kong Disneyland opening in September 2005. Note that in Hong Kong, a subway is an underground tunnel for pedestrians, not for trains.
Trams
You'll find double decker trams bustling along the north coast of the Island. They're slow, but only $2 from beginning to end so they're nice for sightseeing. The Peak Tram runs from Central to Victoria Peak and is a must-see for any tourist; one-way will cost you $20, round-trip is $30.
Buses
English signage on buses is rare, but they're you're only option if you want to travel around the south side of the island. The large double decker buses cover most of the area, and charge by the distance. There are also public minibuses - the ones with the red stripe on top will pick-up and discharge passengers anywhere, the ones with the green stripe follow a fixed route and only stop in designated places. Note that bus route numbers and minibus route numbers are completely different and unrelated.
Ferry
Ferries are abundant in Hong Kong, taking passengers to the various islands in the territory. The most well-known is the Star Ferry, running continuously between Kowloon and Central, for only $2.20 for an upper deck seat.
Taxis
Hong Kong taxis are the cheapest in the world. Fares start at $15, and it's an extra $1.40 for every 200m after the first 2km. If you don't have enough HK dollars, you can negotiate with the driver to accept US dollars or euros.
Cabs come in three colors - Red taxes serve the island and Kolwoon and can also enter the New Territories; Green taxis serve the New Territories exclusively; and Blue taxis serve Lantau exclusively. Beware that the red taxis are based in either Kolwoon or the island, and if you try to hire one to take you to one from the other, they'll charge you twice the tunnel toll so they can get back. There is a $5 baggage fee if the driver handles it.
90% of Hong Kong's population speaks Cantonese. Most residents aren't fluent in Mandarin, but can comprehend it somewhat, and proficiency is increasing. As for English, professionals and those involved with the tourism industry (hotel workers, etc) can speak it well enough, as well as taxi drivers, street vendors, and waitstaff at some restaurants. However, proficiency beyond these groups is limited. All official signs contain English (some exclusively), and most shops will have English signs.
Hong Kong's currency is the Hong Kong dollar, with a fixed exchange rate of 7.8 HKD to 1 USD. The bills come in denominations of $10, $20, $50, $100, $500, and $1000, as well as coins in $10, $5, $2, $1, 50 cents, 20 cents, and 10 cents. You'll find that most people will use their Octopus card in lieu of change, making small purchases move faster. Some shops won't accept $1000 bills due to a counterfeiting problem a couple years ago.
Shopping - you'll find name-brand goods in the shopping malls near Causeway Bay, and cheap open markets are abundant in Kowloon, including Nathan Road, Hong Kong's answer to Beijing's Silk Street. Don't buy electronics - you'll probably be ripped off.
You can get a great view of the city by taking the Peak Tram to the highest point of the Island. Follow the signs from Central Station to find it.
Hong Kong Zoological and Botanical Gardens is small but free, featuring reptiles, primates, a jaguar, and some rare birds and plants.
To get a sense of Hong Kong's traditional heritage, check out Kowloon Walled City Park in Kowloon; Hong Kong Heritage Museum, Tsang Tsai Uk, Che Kung Temple, Man Mo Temple and Fu Shin Street Traditional Bazaar, all located in New Territories; and Po Lin Monastery, featuring the world's largest uncovered, outdoor Buddha. It's free!
Ocean Park is Hong Kong's answer to Sea World, fun for children and adults alike. Beware of loud mainland tourists. Also, Hong Kong Disneyland will open in September on Lantau Island.
Hong Kong offers a variety of regional Chinese cuisine. You'll find traditional and modern Cantonese food everywhere, as well as Teochew and Sichuan styles, and Western restaurants are also abundant. Don't forget to try some of Hong Kong's famous dim sum, often eaten for breakfast or lunch. The touristy restaurants are overpriced and unauthentic - for the real deal, eat Dim Sum in a public housing estate in the New Territories.
"Cooked food centers" are Hong Kong's answer to diners. You'll also find wet markets everywhere, with freshly butchered beef and pork on display, as freshness is important to all Chinese cuisine. There's also a variety of high-class restaurants, located in districts including Lan Kawi Fong, Soho, and Knutsford Terrace.
If you've ever been traveling abroad and missed your friendly neighborhood convenience store, fear no more: 7-Eleven and Circle K are everywhere in Hong Kong.
Hong Kong locals haven't been big on drinking, but you'll find some watering holes in Lan Kwai Fong and Wan Chai, as well as Knutsford Terrace (expensive). In terms of beer, Hoegaarden is widely available, as well as the Chinese Tsing Tsao and Hong Kong Beer. Britons will be happy to find Carlsberg readily available, as there is a brewery in the area.
If you've ever traveled to Japan, room sizes in Hong Kong are about one step up from that. However, there are five-star hotels, including the Peninsula, Mandarin Oriental, and Shangri-La, but keep in mind that lodgings on the Island will run you much more than Kowloon or New Territories. Think of it as staying in Manhattan vs. Brooklyn. A list of Hong Kong hotels is available here.
Hong Kong is a relatively safe city, but like most cities, not free of petty crime. Stay alert and act as you would in any major city and watch your wallet or purse.
Tap water is safe, but it seems that many locals boil the water first simply out of habit.
It's warm in Hong Kong - usually around 95 degrees Fahrenheit - but air-conditioned buildings usually keep it down around 65. Some people experience cold symptoms when they move back and forth between the outside and air-conditioned shopping malls and the like. Some people wear sweaters when they go indoors.
Manners are important to Chinese - but not always the same manners as yours. In Hong Kong, it's okay to talk loud in public, chew loudly, and even point out how fat someone is.
Over 90% of Hong Kong residents have cell phones, and you can use your GSM phone by buying a prepaid SIM card from operators like Peoples and Vodafone. If you need to use the Internet, Pacific Coffee shops offer free access, and some MTR stations have terminals. Cyber cafes are more meant for gaming and less for e-mails and such.