In some cases you may be able to travel to New Zealand without a visa. However, if you want to stay in New Zealand longer than your visa-free conditions allow you need to apply for a Visitor’s Visa. The usual maximum stay for a visitor is nine months. If you wish to return, you do need to spend an equal amount of time out of the country before you can apply.
If you are aged between 18 and 30 you may be eligible to experience life in New Zealand on a working holiday. Find out if your country has a New Zealand Working Holiday Scheme.