Auckland is New Zealand's biggest city.
From the airport
It's easy to hitch a ride to the city center (instead of paying 15 NZD$ for the bus). Just walk out of the airport, go right and find the Shell station and ask around. (Guaka got a ride for himself and another guy, from the first person he asked there.)
Going South, to Hamilton, Taupo, Wellington
Around Auckland there are a lot of highways. You want to get to the gas station on the highway where you can find rides easily.
Apparently there's a gas station on the highway as well.