Your Working Holiday Visa entitles you the right to work in New Zealand for up to a year. Many people work for a few months in order to fund their travels around the islands, others work to save money to take back to their home country. Whatever the reason, it is good to know the types of jobs regularly available for those on the visa.
The stereotypical backpacker job in New Zealand. Fruit picking and packhouse work are the most common, although jobs can be found even in the offseason (bud thinning, tipping, stringing, etc.) Which fruit depends on the location, as well as the season. You could be working with kiwifruit, cherries, strawberries, apples, etc. PickNZ is the de facto resource for times of year, job postings, and most other information related to orchard work. Other resources are Indeed and Backpackerboard
Many jobs in childcare are available for women coming to New Zealand. These seem to be pretty nice jobs for anyone qualified. They often come with pay, accommodation, and occasionally use of the family car. As with any job, be clear on the terms of work, as well as the hours. Indeed and Backpackerboard are two good resources to find these types of jobs.
A well know work exchange program operating worldwide. In NZ, it is no different. You offer yourself to work (typically around four hours a day, five to six days a week) in exchange for food, lodging, and job skills. If this sounds good to you, it is a great way to meet interesting people.
I have heard nothing but good things about the program from my friends who have done (or are currently doing) it. Make sure and read the description carefully, as to understand the exact terms, as well as see where you will be (it could be quite remote!).
That is, working in restaurants, hostels, etc. These vary greatly in terms of pay and accommodation. I have heard mixed results from those I know. Be sure to check out the accommodation, be clear on terms, and make sure your boss is a sane person before agreeing. Here are two places to find hospitality jobs in New Zealand: Indeed and Backpackerboard
You may not get paid, but you will have a base from which to do short trips around the area. Not my cup of tea, but I met two people who really enjoyed the experience.
Construction companies are always looking for more workers, especially in big cities. The pay is decent, the hours are long, and the work is hard. I only know one person who has done this, but his experience is a positive one so far.
No matter which job you end up with, be sure to enjoy the experience!