Entirely agree with Sun777. I would add, look at the list of what is not allowed to be brought into NZ - I'm thinking, particularly under the biohazards category
http://www.mpi.govt.nz/travel-and-re...ms-to-declare/ - and make sure you're not carrying anything like that. This is a MAJOR cause of people having to empty out ALL their baggage upon arrival, and of course, having broken one law often leads on to being questioned about one's whole situation.
Also, thinking about 'we are hearing so many horror stories', consider why people would be telling this, in person or to a newspaper or news station. What has others interested in listening, the tale of hours being questioned, held in segregation, repatriated, etc., or walking gently through arrivals, going through the queue to have your passport stamped, and being told to have a nice day by the official? In other words, you don't get to hear about the thousands and thousands of uneventful journeys, because there's nothing to tell. And officials are always alerted to travellers that they take aside by SOMETHING - it won't ever have been done just on a whim.