Bitcoin trading on localbitcoins.com is the main place New Zealanders use to trade bitcoins, there's an escrow service where they keep the bitcoins safe until the bitcoin seller releases them, it helps knowing that a seller actually has the bitcoins.
They charge a 1% transaction fee so it can be more rewarding and risky to buy and hold the bitcoins or if you want to play it safe you can buy and sell quickly only maintaining a minimal amount of bitcoin.
You can post ads to buy cheap and sell higher than the market rate with a percentage below and above.
For keeping up to date with the market i like to use bitcoinity
Setting up bank accounts in multiple countries is not required but can help being able to trade in multiple countries which normally have much more active bitcoin markets with more competitive buyers and sellers (less spread).
In less competitive areas like New Zealand there can be large differences between buy and sell price and even still there is some skepticism surrounding crypto-currencies, this does present an opportunity for anyone willing to take the risk trusting the traders and trusting bitcoin and undercut the buyers/sellers.
Concerning trust, you must be extremely careful trading bitcoin, the real risk is when selling bitcoin the buyer may make payment with a form of payment that can be reversed like paypal or a bank transfer with a stolen credit card, work must be done to ensure the buyer is who they say they are.
I had a bad experience trading bitcoin where the trader had verified his phone number and email, but not his real name, i sold him two lots of bitcoin totaling $600 AUD, i saw the money in my account and released the bitcoin, alas once the bitcoin is released from escrow he can simply transfer the bitcoin out of his localbitcoins.com wallet, i noticed a few days later that my bank account had current balance $600 available balance $0, localbitcoins.com blocked the account rapidly upon hearing of the scam but they had already got away with the bitcoin.
The solution going forward for me should be to verify someones real name and their intentions via making them upload a picture of their id, face and text saying "for btc purchase from lee" or something to prevent man in the middle attacks
There is no exchange like btcmarkets.com in New Zealand where you place buy and sell orders that are executed automatically, taking out the human aspect and trading with only the exchange reduces risk and so trades on these platforms tend to be very close to 0 margins on the market rate (minus btcmarkets .8% fee).