Hiking in Hong Kong
Hong Kong Island is far more varied than a look at its urban north shore might suggest. From near the upper Peak Tram station, you can stroll to wooded hillsides above a Pokfulam Reseroir - try Pokfulam Reservoir Road, which is closed to most traffic and enters woodland the moment you start on it (opposite the car park). Dragon's Back above Shek O makes for one of the best short hikes in Hong Kong; follow it southwards then, perhaps, catch a bus to Shek O for a meal, and a stroll to the islet of Tai Tau Chau.
The hills just north of Kowloon (eight of the "nine dragons" - the "gau lung") also boast good trails, with views of country and city. Lion Rock has a fairly tough final ascent, but is spectacular when you're on top.
I appreciate this information is extremely brief, but hope it may be useful to you. I'd also recommend buying maps in the Countryside Series, which are available from some HK bookshops, and the Government Publications Centre in Admiralty.
For a wealth of other info, see my site Hong Kong Outdoors.