Mal's suggestions are right on track. Don't be scared to use Taxis for the short trips from Airport Express station to Peak Tram etc if not up to walking. HK Taxis have a flag-fall of HK$18 (about A$3) for first 2km or I think 4 mins. So its not a big investment. At busy times there can be a bit of a wait for Taxis at the station. I had to wait about 40 mins at 7pm one night. But most times its pretty much a walk-up process.
There are also several free shuttle buses for Airport Express passengers that travel various loops around the local area. These are available at both Kowloon and HK stations.
The Airport Express is HK$100 one-way or HK$150 same-day return.
After collecting your bags, and just as you exit the arrivals area into the main airport terminal, there are some very helpful tourist information people. Take a few mins to stop by and chat with them. They all speak very good english and will give you a map and highlight a recommended route for the day. They have people asking just the same thing every day so have some good ideas and will write down the bus numbers, highlight the route on the map, tell you how much things cost, what times they operate etc. Definitely worth stopping by and asking their recommendations, even if you have to wait until they have finished with the person in front. They have brochures for all the regular things you may want to visit. They will even give you a card with the names of common places written in English and Chinese so you can show a taxi driver if they don't understand your pronunciation or accent.
With taxis, the best way to first tell the driver the area (like suburb) you want t go to, and then the name of the place. For example, for the peak tram, say "Central, Peak Tram station" or "Causeway Bay, Star Ferry" and they will know what you mean. The areas will be marked on the map.
If the weather is clear, definitely head up to the peak (tram up) and consider taking the bus back down. The bus takes longer but gives you a good view of the residential areas and wonder views as you wind your way down the mountainside roads.
Since you gave just purchased a new camera, stay away from Mong kok or you might find the same camera for less.
Try eating at a local noodle restaurant. A great feed can be had (by pointing to the picture you like, or some have English menus if you ask) for around HK$50 including a beer (likely Tsing Tao).
