Cool, thank you

I'm just weighing up my options at the mo. I've got a window from the middle of November until Christmas when I'd really like to get some travelling done - one of my friends from uni is living in Japan at the moment, so I'm planning to go see him, but as I'm over in that part of the world I thought I should check out some other places, and I've always wanted to go to NZ! Ideally I'd rather take longer and go from October, but irritatingly my graduation is November 13th....grrrrrr.
I'm looking into getting a round-the-world ticket at the moment - stopping over in a few places, with a longer stay of 7-10 days in NZ and Japan - then I get to explore Japan with my friend and I could maybe pick up a tour in NZ, as otherwise I'll probably be mostly travelling alone...If you've got any recommendations from your travels Alex - planning, and who to go with and just general thoughts, that would be great!
Good stuff, similar thing to what I did.

As for tours, I did my Europe tour with Topdeck and they have started doing NZ and Australia tours this year. Have a look
here. Although they might be a little bit long given your time frame as they don't really spend time in Auckland and Wellington as they are the places you can do yourself fairly easily, but you do probably need an organised group etc for the places in between.
There are also some NZ tour companies although I don't know that much about them having not done them. There's
Kiwi Experience which I've heard is nicknamed the Kiwi Sexperience and is really a party/booze fest! There's also the
Magic Bus which I think is similar to Topdeck. Our driver on the Topdeck tour was a Kiwi and he comes home in the European winter/NZ summer and does the Magic Bus tours and they sounded quite good from what he said. Both of those have hop on hop off tickets aswell so you can get on and off where you like.
As for general advice, it's a lot of common sense really like making sure cameras and wallets are well hidden and not sticking out of bags or back pockets to make pickpocketing easy, don't leave bags lying around out of your sight etc. Also try to backup photos if possible as there could be nothing worse than losing your memory card with your only copies (camera gets stolen, or broken or you drop it over the side of the ferry or something!). I was ridiculously over cautious in this respect but just wanted to ensure I didn't lose anything.
NZ is generally a safe place but like anywhere else there is crime. If you avoid going off the beaten track and hitch-hiking alone you will be fine! There are certain areas of Auckland and the Wellington region you shouldn't go, but as a tourist you're extremely unlikely to be anywhere near them.
When you know, let me know how many days exactly you think you will have in NZ and I can recommend a sort of itinery and the main things to do in the time.