There are a wide range of options to travel to Paihia. Several tourist coach companies offer daily sightseeing services from downtown Auckland including Newmans Coach Lines (http://www.newmanscoach.co.nz/), InterCity Coachlines (http://www.intercity.co.nz/) and Naked Bus (http://nakedbus.com/nz/bus/). These services take around 4 hours and may include rest stops and commentary on local history.
There are also many packaged tours available that include the Bay of Islands in their North Island itinerary. Auckland is the nearest international airport to Paihia. Regional airlines have flights from most of the main centres in New Zealand to Kerikeri airport which is about 20 minutes by car or shuttle van from Paihia.
Rental cars are also a popular choice of transport for overseas visitors.