From picking fruit and milking cows to working in cafes and hotels, there are so many jobs available in New Zealand for travellers to do. That's the beauty of our working holiday visa, you can work in any job, even career related ones.
A great resource for the jobs currently available is the website BackpackerBoard. You can check out the vacancies here. Updated in real time, you are always going to be in the know of hot new jobs as they come up.
Also, have a read about how to apply for a working holiday visa in this article. It really is easy.