In the past 18 months or so I've been doing a fair bit of travelling for work. And I've learned some things about flying with Air NZ...
As long as you have a booking reference, and/or if you have a frequent flier account, you can log in to the website to check your booking and more importantly request your seats.
If you're flying on a Boeing 737-300 (mostly between AKL-WLG-CHC) then the closer to the front you can get the better. There's the obvious benefit of getting off faster when you land, but also, on the AirNZ layout at least, there's increasing amounts of legroom the closer you get to the front. After about row 13 (exit row) it's all the same. My personal preference is a window seat so I can watch the countryside go by, but that's definitely dependent on what you like.
If you're flying on a Bombardier Q300 which are used for flights between major town centres, I have a strong preference for row 1. It's an exit row, so you can't access your hand luggage as well, but I've found that it's often free when you go to request a seat, and again, you get to get off first.
However - if you're flying on a Aerospatiale ATR72 passengers get on at the back, so it's best to sit down that end :) For some reason these are my least favourite planes. I think it's because of the way the wings are almost level with the top of the body of the plane, which makes it look kinda... dumpy.
And then there's the good old 19 seater Beechcraft 1900D. Entry is from the front, but I don't recommend sitting in rows 1 or 2 - there are no windows until row 3. If you've been on these planes, you'll know that there's one seat on either side of the aisle, and at row five the floor goes up and down over a ramp. Which means that in row 6 there's hardly any room to put your hand luggage under the seat in front - and there's no overhead locker so it makes it pretty cramped. Personally I go for 3 or 4 if I have a short connection and need to get off fast, but otherwise I'd go for rows 8 or 9 because your view isn't obscured by the propellors.
My only other hint for now is that the belgian biscuits at the cafe in Auckland airport just opposite the security screening area for gates 28-33 are excellent, and really good when you've had a long day and have one more flight to go :)