You will need a passport and visa to get in Hong Kong, even if you are entering via mainland China. You can apply for a visa at the Chinese embassy or at Hong Kong’s Immigration Department. Details of the entry requirement can be found at the Immigration Department’s website as well.
The official currency of the city is the Hong Kong dollar (HKD), denoted by “$”. So if you see a dollar sign, consider it HKD and not USD. Prices listed in US dollars have the “USD $” sign before them. The standard exchange rate is USD1 = HKD0.80 but banks may offer some slight variations. And airports as well as hotels will offer the least competitive exchange rates of all.
The best place to exchange large amounts is banks and to exchange small amounts is an independent exchange shop. Such shops abound in the tourist places and do not charge the fixed commission as banks do. However, use these shops well within the banking hours to get the best rates. If you have accounts with the HSBC, Standard Chartered or Hang Seng, you may safely and profitably use your ATM debit card instead.