If you have time, try Shenzhen. Apart from having the largest collection of pretty young Chinese girls there is (girl-watching, for the use of) there's a lot to do. Theme parks, museums, a safari park and the shopping's pretty good if there's a memsahib to accommodate.
Yes the peak tram is a must but I'd recommend (if you have the time) just taking a one way trip up, leaving the crowds by doing the short walk up to Victoria Peak Gardens where the views are even more stunning.
After that, either descend by bus (interesting and scenic twisting route) which brings you down to North Point; or even better, try walking down one of the foot paths-either to Aberdeen Harbour or Central.
There is a huge amount to see and do in HK so you'd do well to buy a guide book. There is one series of guide books that tells you what to see if you have 1, 2, 3 etc days in the place. It'll guide you to the more popular and touristy places, but then there's a reason why they're popular!
Avoid the tat (Hard Rock Cafe etc) unless that's your cup of tea, but try to get yourself out to some of the less well-troden parts. Ie, not Central, Tsim Tsa Tsui etc. If you really have the time, try some of the Outlying Islands (but apparently they've built rather a large airport across one or two of them since I was there!)
I'd definitely recommend having a suit tailored, but get yourself measured up early doors. I faffed around trying to find the 'perfect' tailor and then ran out of time. Might be worth doing a little research before you go.
Stayed at Royal Plaza which is vast hotel complex at Mong Kok East with superb chinese restaurant and wonderful chinese hospitality... strongly recommend... working nearby... sat up on the 19th floor watching the chinese kids playing football (badly) before school... not their natural game...
popped into Central and East Tsim Sha Tsui most mornings to mooch around... the Cultural Centre's Art Museum is stunning but especially their bookshop and acquired some heavyweight coffee table chinese art... up to the peak tram... botanical gardens... started walking old peak road... took the usual attitude of "I can walk there easy"... and ballbagged oneself as per usual... up SoHo on foot...
Ate like a Colonial Governor... the HK chinese are humoured, cheeky, fun, and damn impressive workers... will take the wife and kids next year...
Really interesting tips, I may be out there soon and hope to follow them up as well.
How long would you reckon is a good holiday? I'm thinking about the time to get out there vs. expense of staying in what sounds like quite an expensive place, especially if its primarily orientated around shopping and the like.
Is there much to see and do on the outlying islands?
Good tip ref: the clothes, I imagine that going in late September entails sweating through everything you wear!
If going to Victoria Peak, I'd recommend going three times. Once each by Tram, bus and walking, returning the same way as the views and experience are different on the way back. There's not a great deal to see at the top to be honest, though a walk through Pok Fu Lam Country Park is quite pleasant.
The Big Buddha on Lantau is a must. I'm not sure how you get there now - it used to involve a ferry from Central to Mui Wo, another ferry to Tai O, then a long walk. But that was before Lantau was accessible by road.
Cheap clothes can be bought in Mong Kok (as can a lot of other stuff), which makes flying light an option if you're not troubled by wearing "disposable" quality clothes.
I was never really troubled by the humidity in HK, though it is very high. What you will notice is that there's a lot of tacked-on room cooler units on the side of apartment blocks which drip condensate onto the people in the street. It can rain quite a bit, though September is at the end of the rainy (and tornado) season.
If you're walking through Central during rain, there's no need to get very wet. Most of the pedestrian routes link between the office and commercial buildings so your journey could involve crossing several office foyers, but you'll stay dry.
Ocean Park is a fun place to visit. It's a big theme park near Aberdeen.
If there's Rugby on then the Devil's Advocate Pub is a good one.
Drinks in the Mandarin Oriental.
Star Ferry - agree with everybody else - worth doing.
Trip on the Peak Tram a must, great view.
Shopping on Hollywood Road for "antiques" and trinkets. The malls are all the same, seen one, seen em all but this place is good for general shopping of interesting bits and pieces. Chinese Objets dâArt ï¿¼
GOD - Goods of Desire for Homewares. To be fair there isn't that much to do in Hong Kong except shop.
Worth going across the Border to Shenzhen to see that China is a bit of a dump, get your passport stamp and then come back.