I am travelling to Hong Kong and beyond into China in the next couple of weeks, what sim card would you recommend for me to use?
What country are you from? Does your phone have a sim card? Korean and Japanese phones don't appear to use Sim cards. Your Hong Kong / China SIM Card will require a SIM-unlocked GSM 900/1800 compatible international cell phone. If you do not have your own international cell phone you can go somewhere like fortress or Broadway and buy a fairly utilitarian phone for about $100. Phones in Hong Kong are NOT locked, which is probably why the costs of the bigger better models is very high compared to the subsidised phones in the UK (I do not know about the US).
I had some funny conversations about that in Korea where everybody kept using my passport to buy phones. There are about 17 phones in South Korea that operate under my name. A funny story about this was I asked Park why S Korean phones don't use the GSM network that is universal around the world.
He said to me, well if North Korea attacks we can switch the phones off....
Oh... what so if North Korea attacks it means I can't say good bye to my friends and family (I have no family in Korea) they can just switch it off, oh wow great... Though this feature actually exists for the GSM network in that mobile phones will simply be turned off as per government edict.
Anyway I digress.
In Hong Kong I do not recommend a particular brand as almost all of them cost the same come loaded with 200-300 minutes local calls and charge about the same too for both calls inside HK and roaming as well as IDD. So if you buy a $88 sim card it will often have $88 loaded onto it.
Note HK networks charge for receiving a call $0.13.
The competition is so fierce that there is little to choose between either of them, you get peoples, smartone vodaphone (which is one of the most expensive @ $188) 3 network, CSL etc and a million other disposable ones that are $22 but can never be recharged these typically have $100 on them of credit. My dad uses these and his number changes every month or so. It is highly annoying but then my number changes each time I go to HK.
However out of all of them I would recommend CSL purely because I know for a fact that the help line instructions etc are duplicated in English 3 and Vodaphone as well as Peoples don't. Although you can always ask the person in the 7-11 to put the credit on for you if they are not stunningly busy. CSL and Peoples will however roam in China though, it will of course cost more.
As a side though there are some dodgy practices going on where your sim card number is often sold onto marketting companies who will call you on withheld or numbers you are unfamiliar with. This could just be my imagination but 5 minutes after activating my CSL card at the airport I recieved a marketting call. When I had given that telephone number to nobody, although this happened on 3 and vodaphone too.
An oddity you may experience is that the telephone display will not always show CSL as your carrier, it sometimes flips over to vodaphone sometimes 3 sometimes Orange, sometimes a mess or morass of characters this doesn't matter as they all share and share alike the cell phone masts and end up reconciling it between themselves. Though Macau of course is considered to be a completely different country for phone purposes.
China Unicom is popular everywhere sim cards they sell everywhere. and you can get IDD calls for $0.16 a minute to the US and UK. IIRC there is a vendor on the China side of the Lo Wu border.
Don't buy them before you go, they will generally rip you off, as the moment you land in Beijing, HK or Macau you can go to a vending machine or a 7-11 store (everywhere) and buy them much cheaper.
In Hong Kong coverage doesn't matter except in the small villages in the NT, my dad lives in dead zone curiously.
In China in cities it is everywhere in the countryside variable much like the state of play in the US today.