Say you're going overseas for a trip and stopping in Hong Kong or Singapore for a night and you think that this might be a good opportunity to buy a camera. Good idea! You can save yourself a couple hundred dollars and get all the extra wotsits for your camera in one go. Mind you, if you are after a cheap camera then you aren't going to save that much ... and maybe you are better off buying locally.
Know what you want BEFORE you go. Figure out what you want in a camera, and eventually the exact brand and model you want. Tour the local camera shop. Have a list of prices written down! If you are already overseas and have no idea about cameras/prices then talk to sales people in a couple stores and note down the model numbers and the prices, then find an internet cafe and explore DPReview for people's thought on the camera, reviews and most importantly - the USA street price. Convert the price to your currency and the currency of the country that you intend to purchase in. You should be able to check your local stores via the internet. Usually there are at least one or two search engines that will scan for prices in a number of shops, see what bargains you can get locally. Check eBay, the Buy-It-Now prices are a good guide. Have this list of prices written on paper, print outs from a store's web site are good too, but a list of prices and places for the camera you are after works really well. Wave it in the sales person's face. Say things like "aw, for only $50 more I could buy it at home and have local support if something goes wrong and I would be supporting a local business too ... can you throw in a 1Gig memory card / bag at that price?" Trust me, you will be more confident and happier with your purchase after checking that you are getting a good deal.
Don't buy from the airport. Duty free in the international airport in your own country might offer reasonable value (like Brisbane International Airport is actually OK). However the airport in Hong Kong is rubbish, do not buy there; the guys won't haggle and the prices are nothing special at all. Singapore seemed to be better than Hong Kong, but the bargains are always in the city. If you are only in transit through the city then these airport stores are a huge temptation. Don't do it!
Hong Kong airport to the city. If you are in Hong Kong for 4 hours or more then you can easily catch the train in, browse and buy then train back quite quickly and cheaply. Make sure you grab a map of the city on your way to the train which stops inside the airport. Take your luggage to the Kowloon station, this train station has flight check-in facilities so your luggage is all shipped back to the airport and you are issued with your seat! You can then drop off your hand luggage with the good people at the information desk (for a small fee) so you can head into the city unencumbered. The train takes about 20 minutes and I think costs about $20 for a return (same-day) trip. Buses from the station to the city central head in and out very regularly and can be free if you're sneaky about jumping on a bus to a respectable hotel in the heart of HK or you can hire a cab for a few dollars. There are plenty of places to buy stuff, and eat. There are also wonderful little back allies full of hard sellers of fakes, worth a look just for the experience; make sure you know how to haggle!
Don't buy from the first camera store. These camera stores usually try to rip people off by selling for at least RRP (recommended retail price), usually to people who are in a hurry and don't know the going price. Most of these guys will do that, so don't feel bad about talking to them about the camera, what models they think compare to that camera, options for the camera etc and then walking out if you are not sure. You are not wasting their time, you are making sure YOU are getting what you want. I find that I know when I have a good deal by the really good feeling I get about the sales guy, the deal and the camera. If you only have a couple hours then you will have to march around a bit, but purchasing a camera doesn't take long and sometimes a couple hundred meters walk can save you a couple hundred dollars.
Don't fall for the sales tricks. Always have an exit strategy: "OK, I am going to check out some other stores and may be back". Don't fall for "this price is only for right now/tonight", the proper reply to that is "Oh! I will be back when it comes down then". Don't fall for "oh, we don't have that one in stock but we have this better one". Some sales people will have all the camera settings reduced to produce crap images in the hopes you buy a more expensive camera. Sometimes they will claim they don't have the camera you want AFTER you have handed your credit card over and that for only a few more $ you can get this better brand/model; make sure they have the camera IN STOCK before start the payment process. Ask to see it working. Make sure they have NO opportunity to swap the camera after you have tested it. Don't fall for the no-name brand 24 Megapixel camera that is really on 3 Megapixel but is interpolated. Don't fall for the substitute brand, eg "Oh Rectalis is actually a rebadged Minolta". However you DO get different local names, like the Canon IXUS 750 is the same camera as Canon IXY 700, and Canon Powershot SD550. Bloody Canon.
Warranty! International warranty is what you want. Some cameras will have local country warranty only. Having said that, I have never had camera equipment break down on me. Mainly because I don't buy Sony crap. So, for me, warranty is not that important and I can save a couple hundred dollars - should I need warranty then I have to send the thing back to Hong Kong which doesn't bother me.
Extra bits! Lenses, filters, memory cards, camera bag, tripod, spare battery. If you are buying one of the amazing digital cameras with detachable lenses then you are really going to have to hunt around for a good shop that sells lenses at a reasonable price. Filters are an excellent way to protect your main lense on the larger cameras, get a nice neutral density filter and it will take the damage/scrapes instead of the lense. Memory cards are cheap everywhere, no need to buy a big one overseas unless you can get them to include it in the price - a haggling tool, make sure you know your local price as there is usually very little margin on memory, they won't be cheaper in Hong Kong. Always get some sort of bag, even if it is just a slip for your pocket size camera. Scratching the LCD panel sucks. Spare batteries may be a good idea, particularly if your camera chews through the battery. If you can take 150+ pics on one battery charge then you should be alright, but spare charged batteries offer a nice security against missing the key shots. Tripods aren't something that you want to carry around with you everywhere unless you are really keen but everyone should note that keeping the camera steady would cure a LOT of blur shots and resting your arms or camera against something helps heaps.
Finally, don't be afraid to not purchase anything. If you can't find a good bargain, then just hold off and buy off eBay or your local camera store. It may cost a little more but it is better to feel safe and happy about your purchase rather than just purchase something because it is there.
Also check out:
Buying a camera