Dollars and Sense
Hong Kong's official currency is the Hong Kong Dollar, which is pegged to the US Dollar. Its exchange rate has been stable at around HK$7.8 to US$1 over the past 30 years. You don't need to bring much cash to Hong Kong. Enough to cover food, leisure, and transport for the first month or two is best. ATMs can be found nearly everywhere, from a multitude of financial institutions, and the amount withdrawn from your home account will be converted to Hong Kong Dollar at the exchange rate of the transaction date (additional handling fee may be required for the service). Foreigners are free to open bank accounts here (in general, you'll need your student ID card, passport and visa, and proof of residence). Opening a local Hong Kong Dollar bank account is an advisable option if you don't want to deal with the hassle of constantly exchanging foreign currencies. It also facilitates the receipt of remittances from overseas. Larger chain stores usually accept US dollars and Chinese Renminbi in addition to Hong Kong dollars, but the exchange rate may be less favorable.
The bills they are a-changin'...
If you do need to exchange money (cash or travelers' checks), banks generally offer a good exchange rate. An alternative is money changers which can be found in tourist hot spots such as Causeway Bay, Central, and Tsim Sha Tsui. They open longer hours, but generally charge a higher commission.
Think before using the plastic!
Although credit cards issued by overseas card issuers are mostly accepted in Hong Kong, overseas card issuers may charge foreign transaction fees which may make this method of payment more costly. Some outlets may only take cash for smaller payments, and common sense should tell you not to take your credit card down to the local fish market.