You must possess a valid passport.
If you are a citizen from a country other than New Zealand and Australia you must have a valid working visa and IRD number to work in New Zealand.
New Zealand currently has working holiday agreements with the UK, Canada, Chile, The Netherlands, Japan, Ireland, Korea, Germany, Denmark, Sweden, Hong Kong, Italy, Malaysia, and is currently negotiating arrangements with a range of additional countries.
Australians do not need a work permit as a special agreement exists between the countries.
You must be able to satisfy the New Zealand Embassy that your main intention for coming to New Zealand is to holiday, and that employment is an incidental reason for the visit.
Have funds available for your care and maintenance whilst in New Zealand.
Hold a comprehensive medical and comprehensive hospitalisation insurance that will remain current throughout your stay.
Possess a return ticket, or sufficient funds to purchase such a ticket.