It's not too hard to get some sort of visa, just depends on what your job is, qualifications, experience etc. If you work in medicine, IT or something else that is on the skills shortage list, and have some kind of college/university education, then you can get a residency visa quite easily. If you've got a job offer it makes it pretty simple too. Otherwise, you can just show up as a tourist, get a job, and usually sort out a work visa when you're in NZ. You can also get a working holday visa easily enough, which lets you do casual jobs, and from there, find a permanent job, and apply to get a full work visa. After 3 years you can change that to a residency one, and after 7 years, get citizenship. There's only 4 million people in NZ, and one of the biggest issues in the economy is finding skilled workers, so the government encourage immigration. Once you're a citizen, you can live and work in Oz too.
Where to live is a tough one, depends on what you do to earn money really. There's 3 main cities, Auckland, Wellington and Christchurch, and that's where a lot of the work is.
If work doesn't matter, then for me, first choice would be Gisborne, awesome waves, then Taranaki, also got great waves, Dunedin, great waves but bloody cold. But then in the winter, I'd go for somewhere in Canterbury or around Wanaka, because there's great snowboarding/skiing.
Have a look at
www.surf2surf.co.nz - they sell a surf guide to NZ - should give you a good idea of what's what.