Research! Both the internet and television are great resources for your travel preparation. Show on the Travel Channel offer great insight into hotels, restaurants and fun things to do. Specialty travel sites like Fodors or Lonely Planet are invaluable tools in learning about any destination.
Once you have decided how to get there and where to stay, plan a loose itinerary for the different areas of Hong Kong. This allows you to have more time having fun and less time schlepping from A to B. Plan your stops in Kowloon, Central, New Territories together respectively so you aren't spending your days in transit. Consider a side trip to Macau for gambling or spa treatments.
Healthy travelers are happy travelers. Check the Center for Disease Control website for up to date information on illness outbreaks, or shots you may need. A good travel doctor will know what shots you need, and may dive you a prescription to take with you in case something does happen. Hong Kong in particular has Bird Flu concerns, so taking an RX of Tamiflu isn't a bad idea.
Be safe! Go to travel.state.gov to learn about the latest health and safety concerns. Register your personal information an all international trip information if you are concerned about political unrest. Hong Kong is relatively safe, but this site is a good place for current information.
Don't overpack! Hong Kong is a shopping mecca so take advantage! Custom made suits, malls galore, luxury boutiques: with all that Hong Kong has to offer you may not want to bring any luggage at all!
