There are a variety of ways to Feilding including bus, train, shuttle and car. There is also an airport about 15min drive away in Palmerston North
By train
There is a train called trainz scenic (http://www.tranzscenic.co.nz/) that comes into feilding once a day. It starts at $49 from wellington and $69 from auckland
By bus
Bus's are the cheapest way into Feilding. The prices start at $15 one-way from Wellington and $34 from Auckland. There is also a local bus that runs from Palmerston North to Feilding for $5 one-way.
The main bus services that come into Feilding are the Nakedbus (http://www.nakedbus.com), 'Intercity (http://www.intercity.co.nz/) and the Bay Express (http://www.bayxpress.co.nz/). The Nakedbus is usually the cheapest bus service and you can sometimes they have deals for $1.
By car
Feilding is just off state highway 1 about 160 Km north of wellington at a town called Sanson. If your Traveling from Auckland you turn off at bulls about 500km south.