Auckland is New Zealand's biggest city. It is illegal to even walk on any of the motorways, including the on-ramps ($200 instant fine). It is also a very, very big city to walk across.
From the airport
It's easy to hitch a ride to the city center (instead of paying 15 NZD$ 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.) Just make sure you go to the right petrol station. Dan went to the Countdown station, where a lot of the traffic was heading north...
South towards Hamilton, Taupo, Tauranga, Wellington
Around Auckland there are a lot of highways. The multilane roads on which cyclists and pedestrians are excluded are called motorways. The main highway, State Highway 1, is a motorway as it passes through the city and suburbs. It is possible to get rides from on ramps that have a suitable berm for the vehicles to stop. Not all on ramps allow for this. Alternatively, you should get to the "service centre" dedicated to motorway traffic where you can find rides easily. It is between the Papakura and Drury motorway off ramps.
To get to service centre, get a train to Papakura and then outside Papkura train station you can get a bus to take you down great south road I think #475 bus which costs $2. Just get off anywhere around #490 great south rd. If you walk it, it takes about 30-40minutes. Once you are near #490ish there is a st called parkhaven on your right. Walk down park haven rd and follow it as it bends left. At the end of parkhaven there is a grassy area. Look to your right at the wood fence next to the last house. There should be a fairly large hole in the wooden fence which brings you onto the grounds of the service area. However, on the 20th May 2013 the hole was still in the fence, but there was a house being built on the grassy area. It should still be possible to use the hole for a while, but an alternative route to the service centre may need to be sought in the future.
But once you're at the service centre, it's so easy to get a ride :) http://goo.gl/maps/MTUl
A more risky option that you can walk to from the city centre is at the on-ramp at the top of Symons Street, close to the CBD. Walk down the on ramp and there is a big footpath you can stand on and plenty of space for people to stop. Try to get a ride at least to the bombay hills gas station.
You can as well go to the bus station under the sky tower and get a ticket to Bombay junction (about $15) and when you get there, walk across the road to the on ramp which has plenty of space
Apparently there's a gas station on the highway as well. There is also a Countdown petrol station right outside of the airport (closer than the Shell station) where a lot of the traffic seemed to be heading north.
There is a service centre near silverdale turn off on northern motorway before orewa and the toll road. If you can hitch from here there is a good amount of traffic going up far north.
Another good option is to take a bus to Orewa (which is worth visiting on its own) and hitch from there, Buses leave from Wellesley st West, near the sky tower. Take the 994 or 895, a few buses will take you there just read the timetables. Also you can leave from the north shore no problem, bus' leave from takapuna or Akoronga station, which is a bus station right on the northern motorway. Itll cost you maybe 4 dollars to get to Orewa (one can say that theyre going to an earlier stop - Albany for example and itll cost less and god knows nobody will check) Once you get to orewa there is a really good road to hitch from -Hibiscus coast "highway" (its really just a road, there's lots of space to pull over. This road is long and straight and near the beach, To go north head towards the hill, there is a dairy with a car parl where I often hang out and wait for lifts. Once you get going here it's pretty easy to go anywhere north, New Zealand is one of the easiest places in the world to hitch hike, you dont even need a sign, just chuck your thumb out and look friendly.