The visa that you will be able to obtain most quickly will be a temporary work visa, details here.
http://www.immigration.govt.nz/migra...entialwork.htm If your employer is accredited, that would mean he has the 'approval in principle' mentioned, otherwise he will need to provide the information of how he knows there isn't a NZer available to do the job.
Later on or at the same time, you can also apply for Residence under the Skilled Migrant Category
http://www.immigration.govt.nz/migra...nt/default.htm - you'll be using a lot of the same information and proof, but this visa involves more verification, so it takes longer to process.