It really is just a walk with your suitcase to the airport. From there if youre looking for an affordable way to get into the city SuperShuttles is a standard price and a good service. Corporate Cabs are good but they will cost you a good 20 plus more.
We just walked across the road to arrivals and took a taxi from there. But the front desk can call one round. The alternative is to take the SkyBus airport shuttle to/from the terminal. Frequent, cheap and a good service with plenty of stops in the city centre. I can't comment on taxis to the airport as we took the bus.
Corporate cabs - exellent. Service ask for Debbie
Best taxi in Auckland is Corperate Cabs, however if you are just flying in and out walk to the Novotel, as it is 50meters from international and 8 minutes walk from domestic terminal