How to get cheap return flights to Pakistan from NZ?
I use https://www.kayak.com or https://www.skyscanner.co.nz to find the fares, routes and schedules of flights and then book via Airlines directly. Booking via airlines websites directly can protect you better from unexpected delays/cancellations. My personal experience booking via third parties has been a bit rough.
Another technique I found that works well is to find out the cheapest flight from one of the above website and take it to a local travel agent. Ask them if they can beat the price. Sometimes it works and you end up with a really good deal.
Also, If you travel often, it is a good idea to stick to one airline and then add up their miles. Because the round trip between NZ and PK is quite long and you end up piling up these miles very quickly, leading to future discounts.