At the time of writing, INZ asks for at least NZD 1,000 for each month of your stay, or NZD 400 a month if your accommodation is already paid for. Check INZ's visitor visa page for the current figures before applying.
Bank statements are the usual evidence, alongside credit card statements, bank drafts or proof of prepaid accommodation. INZ wants to see that the account is in your name, which bank holds it and what currency it's in, so we translate the account holder details, the bank's name and the currency notation as carefully as the balance.
You also need a ticket out of New Zealand or enough money to buy one, and bank or credit card statements can show that too. If someone is sponsoring your visit, different evidence applies, so check the checklist for your situation.