New Zealand is an island nation and as a result of its geographic isolation has not been exposed to many pests and diseases that are present in the rest of the world. New Zealanders would like to keep it like this and as a result have quite strict agricultural and fisheries requirements for entry - more so than you may encounter for most other countries.

Everyone entering NZ is required to fill out a declaration form which has a number of questions related to food substances, animal and vegetable products as well as more standard questions on money etc. Please answer all questions truthfully - if you don't it is highly likely that you will be found out and instant fines of normally NZ $200 or more can apply at the border - if not more serious charges. MAF and Customs X ray all baggage now as well as using sniffer dogs, so the apple you have in your hand bag is very likely to be found. If in doubt about anything - DECLARE IT.  

Other requirements are much more standard - 1 litre of spirits is permitted, but there is also a special over allowance on spirits of up to 3 litres if you are not bringing in more than NZ $700 worth of dutiable items.

Leaving New Zealand is very similar to most other countries. Beginning in early 2009, if you depart from Aukland airport, your departure tax is included in the "Tax & Fees" section of your airfare.  However the departure tax (NZD 25) is not yet included at other airports and must be paid separately.  They will give you a sticker (generally put on your boarding pass) which proves that you have paid departure tax.