One of the first orders of business for the working holiday maker is to open a local bank account. However, even for someone that is staying for a shorter period of time and not planning to work very often, a New Zealand bank account can be very handy…and, even though the banks claim you need a permanent address, they will often let you use the address of the hostel where you are currently staying, or even the address of the bank where you are applying. I spent about a month in New Zealand without a local bank account before I got sick of the fluctuating exchange rate (the US dollar had, at this point, lost 6c per NZ dollar since I'd arrived) and the excessive bank fees. Unfortunately, these days it is very difficult to find a bank or credit card provider that doesn't charge a foreign exchange fee; in my case, I was getting charged about 3% extra per transaction. These fees appeared separately from the original charge on my bank statement, so every time I checked my account, I could see all of the money that I was losing.
A local bank account has none of these drawbacks. Once you withdraw the money from your home account (which I did regularly, as the ATMs would only dispense $800/day) and deposit it into your local account, you know the exact amount of money that you have and don't have to worry about it slowly disappearing because the US dollar is worthless. Also, there are no fees for normal transactions in stores and no ATM fees provided you use your bank's ATM. I found that an added bonus of having a local account was that I could use the EFTPOS facilities in stores, meaning I could use my PIN number rather than having to press "credit" and then sign.
There are a number of banks to choose from. If you are a Bank of America customer, I recommend going with Westpac, who partner with Bank of America and do not charge BofA customers any fees for using their ATMs. Westpac accounts normally incur about a $3/month fee, but if you stop paper bank statements, the account is free. They are also one of the largest banks in the country, meaning that most towns have their ATMs. The only bank that I saw with more ATMs than Westpac was the Bank of New Zealand. A simple everyday checking account with BoNZ costs $5/month. ANZ also has quite a few branches throughout the country, as do ASB, KiwiBank and HSBC.
An important note for Australian travelers: Westpac and ANZ may have the same name as banks in Australia, but they do not operate under the same banking system, so even if you have a Westpac account in Australia, you cannot go into NZ Westpac branches and make deposits, etc. However, you can use a Westpac ATM without paying any extra fees.