Obvioulsy flats in a desirable area would be preferable and they will tend to appreciate more in good times. But you're also going to pay a lot more...which in your case means a larger downpayment than you may be comfortable with...
Another interesting investment option is to look for a flat in a good older building with lots of elderly residents. You find one that hasn't been renovated in at least 10 years and put a bit of money to clean it up. You will then reap the double profit of spiffing up a place and waiting for a better market.
Otherwise, you can stick with established developments in good areas, I would recommend the upper part of Wanchai, Happy Valley, Causeway Bay, Sheung Wan and the Quarry Bay/Tai Koo, Kornhill area, the upper parts of Tin Hau and North Point... A good thought about Western District properties since they might be cheaper with good appreciation potential since the MTR will be going that way in a few years.
I'd say the minimum ratio of finding a good place is to visit at least 10 for each one you intend to buy in an area. Try to talk to some residents and maybe the guards to get a feel for the clientele of the building and whether there are problems(vermin, security, leaks, water pressure etc...) Never trust any agents, they get their money from the sellers and not buyers... Be careful about leaving yourself a good safety margin... Interest rates are very low now but it's good to look at scenarios where interest rates are at 8-9% to see whether you can sustain this for an extended period or if you can't find tenants for a few months...
I'm certainly hoping to cash in from this little financial hick up...I'm hoping for a market rebound in the spring/summer. I flipped a property last spring when it was quite high so I'll be on the hunt for some deals in 2009.