Depending on the nationality, people from most countries can enter Hong Kong without a visa and stay for between 7 days and 6 months. You should check with the Chinese embassies and consulates in your country to confirm the visa requirements.
Generally, there are no vaccination requirements, but you should check with your carrier or the Chinese embassies and consulates before you depart. However, if there is an epidemic (such as bird flu or SARS a few years ago), stringent procedures are enforced at airports and other points of entry to check the health condition of people coming into the territory.
Hong Kong is a compact and busy cosmopolitan city. As it has a public transportation system with broad coverage, you can move about fairly easily even if you are carrying your luggage. Shops are everywhere; so you can get daily necessities you need in case you forget to bring them with you.
If you come during those months with more rain (about April to September), it is wise to bring along an umbrella or raincoat.
Communication by fixed-line telephones, mobile phones, mail or the internet are all available. Fixed-line phones are available from public booths and hotels for a charge, but with widespread use of mobile phones, public phone booths are not easy to find. Hong Kong mobile phone operators have roaming agreements with their counterparts in most countries overseas, which allow visitors to use their mobile phones in Hong Kong. Alternatively, visitors can buy phone cards which allow them to call overseas at a much lower cost.
Hong Kong is a safe city even at night, but like anywhere else, you should exercise caution and common-sense.
Useful contact numbers: 1. Emergency police, fire and medical services - 999; 2. Hong Kong International Airport - 21810000; 3. Hong Kong Immigration Department - 28246111; 4. Telephone directory enquiry - 1081; 5. Hong Kong Tourism Board hotline - 25081234.